I am DM'ing Dragon of Icespire Peak (DoIP) for a party of 5 characters - human wizard, dwarf fighter, elf cleric, halfling rogue, and half-orc bard. (Kind of vanilla, I know, but my players include my two young nephews and my young son who have never played before so we kept it pretty simple. The half-orc is my adult niece.) They're 3rd level now and just had a pretty easy time dispatching orcs at Butterskull Ranch and ankhegs at the Logger's Camp. I'm using xp to advance their levels, but even if they do the side adventures (Shrine of Savras, Tower of Storms) I'm going to have a tough time getting them to 6th level on xp alone, before they face Cryovain at the end. However, I'm starting to think maybe they don't have to be 6th level to face him/her (I guess the dragon's gender is up to the DM?). Could five 5th-level characters reliably defeat Cryovain as written in the adventure after a tough fight, or would it be a toss-up with potential death of one or more characters? (I'd hate for my nephews or son to lose their characters.)
I would agree that the setup might be considered a bit of a pushover. I might suggest that you not oversell this encounter, as it will underperform for your party, especially if they have the Dragon Slayer. Understand that I'm not advocating for making this too significant a challenge considering your party makeup, but I'm going to assume that someone in the group will make a connection/conclusion between the ability of this Young White Dragon, and the number of Orcs that it displaced. If that connection is made, the players may feel a bit disappointed at how quickly, and easily, the battle ended.
As for your concern about PC death, you can control who takes what hits, and who gets targeted by the dragon's breath weapon. You should have a feel for how much damage each PC can, and has taken during an encounter. Even as written, it's possible, but highly unlikely, for a PC to drop by the breath weapon, or a lucky crit on a bite. So long as the dragon doesn't focus fire on one target, there should be a very limited chance for a PC to drop. I don't advocate for fudging dice rolls, but I do advocate for homebrewing attacks and monster HP. If you feel that it would serve your game better, make adjustments to the HP of the creature, save DCs, or the amount of damage it's attacks and breath weapon does.
You're the best judge of what your party thinks is fun. Be it how dangerous, or easy the encounters are. Change anything in the encounter game world to achieve that end.
“Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.” - Mark Twain - Innocents Abroad
If anything, you might have to boost Cryovain. It might be ok if the PC had to fight the stone cold reavers beforehand but Icespire Hold is kind of bare and they will overwhelm the dragon if they fight him without tiring first. A single CR 6 monster should be a normal encounter to your party according to Xanathar and encounter difficulty is kind of iffy when it is one against many due to action economy. You will have to use his max health at a mininmum and even then it might be underwhelming.
Besides, the big jump in a character's power is from level 4 to 5. The main difference between a level 5 and 6 in terms of fighting effectiveness is that the level 6 has a bit more endurance (as in health, spell slots, rages, etc) so for a single fight encounter there shouldn't be that much of a difference whether they are level 5 or 6. Well, unless they are a fighter, then they may use the ASI for a feat or something or a spellcaster might get a spell that helps more than the one they chose for five, like Earthbind, Fly or absorb elements if it was a damaging one or a combat ine if it wasn't.
I had a party of 5 x sixth level experienced characters and replaced cryovain with a young blue dragon and modified the plot (using some great suggestions I found) to tie the dragon to the cult of Talos and the orcs in a more cohesive narrative. Cryovain would have been a push over for this party. The young blue dragon had a couple of more challenging moments but I think only one of the characters was knocked unconscious.
In your case, 5 x 5th level characters should be ok though it may depend a lot on luck.
Cryovain's breath weapon is 10d8 (45 average) cold damage in a 30 foot cone and a DC15 con save for 1/2 damage. Only one of the party is proficient at con saves - which for a 16 con fighter would give them a +6 - they fail 40% of the time and most of the rest, assuming a 14 con and +2 to the save will fail on a 12 or less or about 60% of the time. An typical d8 class with 14 con would have 38 hit points at 5th level. You can see the problem - one breath that happens to hit the entire party and some average luck on saves and 1/2 the party is likely down. The breath also recharges on a 5-6.
The dragon also makes 3 melee attacks in a turn - one bite average 19 damage and two claws - average 11 each (all +7 to hit). If all three hit - that is an average damage of 41 which is also greater than the 38 average hit points (or less) of 4/5 of your party. Whether they all hit is a matter of luck and how good their AC is. AC depends on what equipment you have made available or allowed to be found and how good the players are at making the most of the armor and stats of their characters.
So there are several things to consider with how well the encounter would go and some of it has to do with luck and the tactics you choose to use as the dragon.
Thanks. You mean they'll be fine at 5th-level, right?
Correct.
I ran the encounter for six 6th-level characters who successfully recruited the Stone-Cold Reavers who survived their initial skirmish. My version of Cryovain had the legendary actions of an adult, toned down for his challenge rating and ability scores. Overall, his CR still jumped to...I want to say 10, so his proficiency bonus also went up. The idea was to follow the guidance in Xanathar's for solo creatures challenging a party, but it only worked for legendary creatures. I did not give him any legendary resistance, but I did give him some innate spellcasting in the form of a once per day fog cloud; up-casted to 3rd level so it had a 60-foot radius. The tempest cleric then used gust of wind to disperse it in chunks; which was the idea. I got them to burn resources while still creating some hazardous terrain. Not all of the cloud was gone, so Cryovain was passing in and out of view. And he kept succeeding on his saving throws for concentration.
Overall, the fight lasted 5-6 rounds. People went down, but the players won in the end.
In the future, I'll make his spell is sleet storm and telegraph it early with a random encounter so someone can have dispel magic ready.
I am running this very campaign for a party of 5 myself and have had to seriously up the challenge level, either by increasing the number of hit points on the monsters, or increasing the numbers significantly.
I am already anticipating having to make the final fight with Cryovin significantly harder to make it challenging.
Thanks so much for the responses and suggestions, everyone! I think I will keep Cryovain as a white dragon since that's the way I've been hyping him/her (still deciding on gender, based on a storyline I'll add - either a male seeking to claim territory or a female feeding and protecting her young). It's been crazy how many times the d20 roll for Cryovain's whereabouts happened to coincide with where the party was, so the party has seen the dragon a number of times now - and the most recent time, the dragon saw a couple of them too, though it opted to carry off one of Big Al Kalazorn's stray horses rather than one of the party members. Anyway, thanks again for the tips and ideas. I plan to keep the party at level 5 and yes, choose the dragon's targets carefully during the battle. Happy DM'ing, all!
Thanks so much for the responses and suggestions, everyone! I think I will keep Cryovain as a white dragon since that's the way I've been hyping him/her (still deciding on gender, based on a storyline I'll add - either a male seeking to claim territory or a female feeding and protecting her young). It's been crazy how many times the d20 roll for Cryovain's whereabouts happened to coincide with where the party was, so the party has seen the dragon a number of times now - and the most recent time, the dragon saw a couple of them too, though it opted to carry off one of Big Al Kalazorn's stray horses rather than one of the party members. Anyway, thanks again for the tips and ideas. I plan to keep the party at level 5 and yes, choose the dragon's targets carefully during the battle. Happy DM'ing, all!
All my dragons are genderless, so they go by them/they pronouns.
Yeah, the whole rolling for where Cryovain is can lead to some nutty scenarios. I am running DoiP and LMoP combined, with Cryovain switched to a blue dragon and Venomfang and him being rivals, so I am rolling for both. The rolling made it so that they ended up fighting several times, sometimes two days in a row, and Cryovain attacked Phandalin like six times. I ended up making it so that it was like that because Venomfang kept sending minions after Cryovain while pretending that they were from phandalin so that Cryovain would be weakened by fighting the town and Venomfang could finish him off. Though in the end, given how many times Cryovain attacked, the town ended up investing on ballistas and the players grounded cryovain with Earthbind while it attacked the town, so they dogpiled him while the guards kept shoting at it.
Note: Either don't do that or give the dragon a teleporting spell. By the end of it you had to feel sorry for the dragon, as he ended up being killed by random guard #3.
A young white dragon is pretty much a walkover encounter for five level 5 characters. If they're long-rested, they'll kill it in the first turn of combat, and if not, they'll probably kill it in the second turn.
A young white dragon is pretty much a walkover encounter for five level 5 characters. If they're long-rested, they'll kill it in the first turn of combat, and if not, they'll probably kill it in the second turn.
I think you overstate how fast it will be (I think a typical level 5 party will need two rounds even if rested) but I wouldn't expect it to be terribly dramatic. It's going to fare better than most CR 6s, though, because it has the dragon fudge factor (compare it to a chimera. Same CR, but the dragon has +3 AC, +19 HP, +14 breath weapon damage, +9 multiattack damage, 4 save proficiencies).
young white dragon vs. non-optimised, long rested level 5 party. A few simple example character turns
Level 5 fighter, no magic items: +7 to hit vs. AC17, 55% hit rate. Assume one attack hits. Longbow, 8 damage average. 2 attacks, plus 2 further attacks from action surge, most likely going to do 16 damage in the first turn. If Battlemaster, add a further 8 damage from using 2 manoeuvres, so call it 24 damage in first turn of combat. If the PC is optimised, this will be higher.
Level 5 Wizard, no magic items: Fireball, save DC= 8+4+3=15. YWD has +3 to Dex save, so will fail more than 50% of the time, so assumed failure, 28 damage, or 14 damage 45% of the time.
Level 5 Rogue, no magic items: Shortbow +7 to hit vs AC17, 55% hit rate. Assume sneak attack, damage is 4d6+4, 18 damage on hit. The rogue only gets one attack, but has ways of generating advantage but this is admittedly a bit swingy and situational.
Let's call 18 damage the low, 28 damage the high, so 23 damage per character is a reasonably low expectation. 5 x 23 damage is 115 and the YWD has 133 hit points. On very average dice rolls, with a very average party, the dragon will have 18 hit points going into turn 2, and with +0 initiative we'd expect the PCs to get a couple more shots in before the dragon takes its turn, so it will get to take one turn before being reduced to a pile of bones and scales.
The hit points on 5e monsters are so low as to be a joke in many situations. If the party doesn't have Action Surge and its 3rd level slots it will go better for the dragon, of course. But it's definitely dead in the 2nd turn of combat at the very latest. On average rolls with average characters and a single critical hit, it's very, very likely to go down on turn 1.
young white dragon vs. non-optimised, long rested level 5 party. A few simple example character turns
Level 5 fighter, no magic items: +7 to hit vs. AC17, 55% hit rate. Assume one attack hits. Longbow, 8 damage average. 2 attacks, plus 2 further attacks from action surge, most likely going to do 16 damage in the first turn. If Battlemaster, add a further 8 damage from using 2 manoeuvres, so call it 24 damage in first turn of combat. If the PC is optimised, this will be higher.
Level 5 Wizard, no magic items: Fireball, save DC= 8+4+3=15. YWD has +3 to Dex save, so will fail more than 50% of the time, so assumed failure, 28 damage, or 14 damage 45% of the time.
Level 5 Rogue, no magic items: Shortbow +7 to hit vs AC17, 55% hit rate. Assume sneak attack, damage is 4d6+4, 18 damage on hit. The rogue only gets one attack, but has ways of generating advantage but this is admittedly a bit swingy and situational.
Let's call 18 damage the low, 28 damage the high, so 23 damage per character is a reasonably low expectation. 5 x 23 damage is 115 and the YWD has 133 hit points. On very average dice rolls, with a very average party, the dragon will have 18 hit points going into turn 2, and with +0 initiative we'd expect the PCs to get a couple more shots in before the dragon takes its turn, so it will get to take one turn before being reduced to a pile of bones and scales.
The hit points on 5e monsters are so low as to be a joke in many situations. If the party doesn't have Action Surge and its 3rd level slots it will go better for the dragon, of course. But it's definitely dead in the 2nd turn of combat at the very latest. On average rolls with average characters and a single critical hit, it's very, very likely to go down on turn 1.
Level 5 fighter (using action surge): we expect 2.2 hits for 8.5 each, total 19. Add 9 for a battle master.
Level 5 wizard (using fireball): the dragon has a 45% chance to save so expected damage is 22
Level 5 rogue (using shortbow and steady aim for advantage): 80% chance to hit for 18, so expected damage is 14
Level 5 cleric: guiding bolt maybe? 6d6 with a 55% chance to hit (12); we'll value the advantage at 4 (25% chance to turn a 16 point miss into a hit).
That's 80 damage across 4 characters, so figure 100 for 5, and the dragon dies somewhere during round 2, which is what I said (magic weapons will boost things slightly, but probably not by 33). All of this assumes that the PCs have a clear line of fire on the dragon and can fire at will, which is not guaranteed (remember a white dragon has a Burrow speed).
Now, this ignores the dragon attacking. The fighter has 44 hp and Con save +5, the cleric and rogue are at 38 and +2, the wizard is at 32 and +2 (but likely has absorb elements), so if the dragon can breathe on two PCs (how likely this is depends on the lair layout) it's probably going to one-shot one of them. That's going to immediately reducing the party's damage output. That probably won't cause the encounter to go past 2 rounds unless the dragon gets lucky on initiative there's something additional going on (if the dragon was relaxing buried in a snow bank and makes a stealth check, which isn't super likely but certainly could happen, things could go really badly for the PCs; contrariwise if you assume the dragon isn't paying attention at all and lets the PCs prebuff with Aid, Bless, etc, one round becomes reasonable).
If you want an interesting encounter, you'll either need to substantially buff the dragon or give it a beneficial environment, but unless you play monsters as "it takes a pose to to let you conveniently shoot at it", it's not that trivial.
Incidentally, the problem with monster hp is really that PCs do too much damage. A typical front-loaded monster does something like 50% of hit points on round 1, 25% on round 2-3, with enough miss chance that it takes around 5 rounds to beat itself. If PCs were held to the same standards, they'd be doing something like 10 damage per PC on round 1, and 5 in subsequent rounds.
Incidentally, the problem with monster hp is really that PCs do too much damage. A typical front-loaded monster does something like 50% of hit points on round 1, 25% on round 2-3, with enough miss chance that it takes around 5 rounds to beat itself. If PCs were held to the same standards, they'd be doing something like 10 damage per PC on round 1, and 5 in subsequent rounds.
I liked your breakdown, and I think it's pretty accurate.
The dragon may one shot one of the PC's with its breath weapon, for sure. It needs to target those that have not taken a turn yet to have a significant impact and almost certainly still goes down turn 2 regardless as you say. This is also considering the party we've used as examples has no magical items, and everything has been done as a ranged attack (assuming the dragon is flying), the PCs don't attempt to surprise the dragon, and so on.
Re: hit points... it can't be said that the problem is the PC's doing too much damage, because monster hit points only have relevance in terms of how much damage they can take from the PCs, so the monster hp needs to be in line with expected damage outputs, not the other way around. The devs have tried to get around this by front-loading damage as you say, which means that fights typically end in 2-3 turns of combat. Personally I think this makes for unsatisfying encounters, and the whole random recharge of breath weapons and the like lends itself to potential TPKs if the dragon recharges on turn 2 and turn 3 (1 in 9 chance).
It also doesn't factor in that PCs aren't meant to have everything available and the daft 6-8 encounters idea, which only works if your entire game is nothing but dungeon crawls. I have some sympathy for the devs in trying to balance these things out, since you just can't know what level the party is, how many characters, how many NPC supports, how rested the party is and so on but the monsters are designed in a way that doesn't work for epic combats. It's a brief burst of cooldown ability popping and the BBEG is done in 12 seconds.
I dunno why I complain about this, I homebrew 90% of my monsters anyway /shrug
I would say, if these are children playing, then make sure the cleric has the components required for a resurrection spell, it isn't detailed anywhere in the adventure i am pretty sure but I made sure that my party found diamonds, enough to give the cleric 2 casts of revivify, and out of game (because they where all new) I mentioned to the cleric they might want to have a look at spell components before the party just cashed in on things they had found.
I also put a higher level priest in the town who was available to cast a higher level resurrection spell just in case, this would have required a bit of adventuring after to do some things to help this priest out, but it just means that a bad dice roll wont auto kill a character with no chance of getting them back.
Re: hit points... it can't be said that the problem is the PC's doing too much damage, because monster hit points only have relevance in terms of how much damage they can take from the PCs, so the monster hp needs to be in line with expected damage outputs, not the other way around.
The big reason PC damage is a problem is because the NPC party is something most DMs like to use at some point, and NPCs should at least be a semi-convincing emulation of PCs. This puts constraints on how tough you can reasonably make them. However, if you just put a party of PCs up against their perfect clones (which is by definition a coin-flip fight, way beyond deadly, and thus should take longer than a standard fight -- probably 4-5 rounds) you're going to have multiple characters down by the end of the first round. If PCs had an offense to hp ratio more like monsters, a 3 round fight would in fact be an "everyone is drained but probably not dead" fight.
An interesting thing to try might be an "Everyone and everything has max hp". It doesn't really change the overall difficulty of fights, but it makes it more practical to have an ordinary fight (drains resources and damages PCs, but the PCs are going to reliably win) last three rounds, and a super scary fight last four to five.
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I am DM'ing Dragon of Icespire Peak (DoIP) for a party of 5 characters - human wizard, dwarf fighter, elf cleric, halfling rogue, and half-orc bard. (Kind of vanilla, I know, but my players include my two young nephews and my young son who have never played before so we kept it pretty simple. The half-orc is my adult niece.) They're 3rd level now and just had a pretty easy time dispatching orcs at Butterskull Ranch and ankhegs at the Logger's Camp. I'm using xp to advance their levels, but even if they do the side adventures (Shrine of Savras, Tower of Storms) I'm going to have a tough time getting them to 6th level on xp alone, before they face Cryovain at the end. However, I'm starting to think maybe they don't have to be 6th level to face him/her (I guess the dragon's gender is up to the DM?). Could five 5th-level characters reliably defeat Cryovain as written in the adventure after a tough fight, or would it be a toss-up with potential death of one or more characters? (I'd hate for my nephews or son to lose their characters.)
Cryovain is a lone CR 6 creature that's designed to be tackled by two 6th-level characters: one player character and one sidekick.
Your five players will be fine.
Thanks. You mean they'll be fine at 5th-level, right?
I would agree that the setup might be considered a bit of a pushover. I might suggest that you not oversell this encounter, as it will underperform for your party, especially if they have the Dragon Slayer. Understand that I'm not advocating for making this too significant a challenge considering your party makeup, but I'm going to assume that someone in the group will make a connection/conclusion between the ability of this Young White Dragon, and the number of Orcs that it displaced. If that connection is made, the players may feel a bit disappointed at how quickly, and easily, the battle ended.
As for your concern about PC death, you can control who takes what hits, and who gets targeted by the dragon's breath weapon. You should have a feel for how much damage each PC can, and has taken during an encounter. Even as written, it's possible, but highly unlikely, for a PC to drop by the breath weapon, or a lucky crit on a bite. So long as the dragon doesn't focus fire on one target, there should be a very limited chance for a PC to drop. I don't advocate for fudging dice rolls, but I do advocate for homebrewing attacks and monster HP. If you feel that it would serve your game better, make adjustments to the HP of the creature, save DCs, or the amount of damage it's attacks and breath weapon does.
You're the best judge of what your party thinks is fun. Be it how dangerous, or easy the encounters are. Change anything in the
encountergame world to achieve that end.“Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.” - Mark Twain - Innocents Abroad
If anything, you might have to boost Cryovain. It might be ok if the PC had to fight the stone cold reavers beforehand but Icespire Hold is kind of bare and they will overwhelm the dragon if they fight him without tiring first. A single CR 6 monster should be a normal encounter to your party according to Xanathar and encounter difficulty is kind of iffy when it is one against many due to action economy. You will have to use his max health at a mininmum and even then it might be underwhelming.
Besides, the big jump in a character's power is from level 4 to 5. The main difference between a level 5 and 6 in terms of fighting effectiveness is that the level 6 has a bit more endurance (as in health, spell slots, rages, etc) so for a single fight encounter there shouldn't be that much of a difference whether they are level 5 or 6. Well, unless they are a fighter, then they may use the ASI for a feat or something or a spellcaster might get a spell that helps more than the one they chose for five, like Earthbind, Fly or absorb elements if it was a damaging one or a combat ine if it wasn't.
Five 6th level characters will have an easier time for sure. Some DM even replace it for a blue dragon to up the challenge.
I had a party of 5 x sixth level experienced characters and replaced cryovain with a young blue dragon and modified the plot (using some great suggestions I found) to tie the dragon to the cult of Talos and the orcs in a more cohesive narrative. Cryovain would have been a push over for this party. The young blue dragon had a couple of more challenging moments but I think only one of the characters was knocked unconscious.
In your case, 5 x 5th level characters should be ok though it may depend a lot on luck.
Cryovain's breath weapon is 10d8 (45 average) cold damage in a 30 foot cone and a DC15 con save for 1/2 damage. Only one of the party is proficient at con saves - which for a 16 con fighter would give them a +6 - they fail 40% of the time and most of the rest, assuming a 14 con and +2 to the save will fail on a 12 or less or about 60% of the time. An typical d8 class with 14 con would have 38 hit points at 5th level. You can see the problem - one breath that happens to hit the entire party and some average luck on saves and 1/2 the party is likely down. The breath also recharges on a 5-6.
The dragon also makes 3 melee attacks in a turn - one bite average 19 damage and two claws - average 11 each (all +7 to hit). If all three hit - that is an average damage of 41 which is also greater than the 38 average hit points (or less) of 4/5 of your party. Whether they all hit is a matter of luck and how good their AC is. AC depends on what equipment you have made available or allowed to be found and how good the players are at making the most of the armor and stats of their characters.
So there are several things to consider with how well the encounter would go and some of it has to do with luck and the tactics you choose to use as the dragon.
Correct.
I ran the encounter for six 6th-level characters who successfully recruited the Stone-Cold Reavers who survived their initial skirmish. My version of Cryovain had the legendary actions of an adult, toned down for his challenge rating and ability scores. Overall, his CR still jumped to...I want to say 10, so his proficiency bonus also went up. The idea was to follow the guidance in Xanathar's for solo creatures challenging a party, but it only worked for legendary creatures. I did not give him any legendary resistance, but I did give him some innate spellcasting in the form of a once per day fog cloud; up-casted to 3rd level so it had a 60-foot radius. The tempest cleric then used gust of wind to disperse it in chunks; which was the idea. I got them to burn resources while still creating some hazardous terrain. Not all of the cloud was gone, so Cryovain was passing in and out of view. And he kept succeeding on his saving throws for concentration.
Overall, the fight lasted 5-6 rounds. People went down, but the players won in the end.
In the future, I'll make his spell is sleet storm and telegraph it early with a random encounter so someone can have dispel magic ready.
I am running this very campaign for a party of 5 myself and have had to seriously up the challenge level, either by increasing the number of hit points on the monsters, or increasing the numbers significantly.
I am already anticipating having to make the final fight with Cryovin significantly harder to make it challenging.
Thanks so much for the responses and suggestions, everyone! I think I will keep Cryovain as a white dragon since that's the way I've been hyping him/her (still deciding on gender, based on a storyline I'll add - either a male seeking to claim territory or a female feeding and protecting her young). It's been crazy how many times the d20 roll for Cryovain's whereabouts happened to coincide with where the party was, so the party has seen the dragon a number of times now - and the most recent time, the dragon saw a couple of them too, though it opted to carry off one of Big Al Kalazorn's stray horses rather than one of the party members. Anyway, thanks again for the tips and ideas. I plan to keep the party at level 5 and yes, choose the dragon's targets carefully during the battle. Happy DM'ing, all!
You can always use a blue dragon but reflavor it as a white dragon, changing its Dragon Breath damage & immunity to cold and give it Ice Walk trait.
All my dragons are genderless, so they go by them/they pronouns.
Yeah, the whole rolling for where Cryovain is can lead to some nutty scenarios. I am running DoiP and LMoP combined, with Cryovain switched to a blue dragon and Venomfang and him being rivals, so I am rolling for both. The rolling made it so that they ended up fighting several times, sometimes two days in a row, and Cryovain attacked Phandalin like six times. I ended up making it so that it was like that because Venomfang kept sending minions after Cryovain while pretending that they were from phandalin so that Cryovain would be weakened by fighting the town and Venomfang could finish him off. Though in the end, given how many times Cryovain attacked, the town ended up investing on ballistas and the players grounded cryovain with Earthbind while it attacked the town, so they dogpiled him while the guards kept shoting at it.
Note: Either don't do that or give the dragon a teleporting spell. By the end of it you had to feel sorry for the dragon, as he ended up being killed by random guard #3.
A young white dragon is pretty much a walkover encounter for five level 5 characters. If they're long-rested, they'll kill it in the first turn of combat, and if not, they'll probably kill it in the second turn.
I think you overstate how fast it will be (I think a typical level 5 party will need two rounds even if rested) but I wouldn't expect it to be terribly dramatic. It's going to fare better than most CR 6s, though, because it has the dragon fudge factor (compare it to a chimera. Same CR, but the dragon has +3 AC, +19 HP, +14 breath weapon damage, +9 multiattack damage, 4 save proficiencies).
young white dragon vs. non-optimised, long rested level 5 party. A few simple example character turns
Level 5 fighter, no magic items: +7 to hit vs. AC17, 55% hit rate. Assume one attack hits. Longbow, 8 damage average. 2 attacks, plus 2 further attacks from action surge, most likely going to do 16 damage in the first turn. If Battlemaster, add a further 8 damage from using 2 manoeuvres, so call it 24 damage in first turn of combat. If the PC is optimised, this will be higher.
Level 5 Wizard, no magic items: Fireball, save DC= 8+4+3=15. YWD has +3 to Dex save, so will fail more than 50% of the time, so assumed failure, 28 damage, or 14 damage 45% of the time.
Level 5 Rogue, no magic items: Shortbow +7 to hit vs AC17, 55% hit rate. Assume sneak attack, damage is 4d6+4, 18 damage on hit. The rogue only gets one attack, but has ways of generating advantage but this is admittedly a bit swingy and situational.
Let's call 18 damage the low, 28 damage the high, so 23 damage per character is a reasonably low expectation. 5 x 23 damage is 115 and the YWD has 133 hit points. On very average dice rolls, with a very average party, the dragon will have 18 hit points going into turn 2, and with +0 initiative we'd expect the PCs to get a couple more shots in before the dragon takes its turn, so it will get to take one turn before being reduced to a pile of bones and scales.
The hit points on 5e monsters are so low as to be a joke in many situations. If the party doesn't have Action Surge and its 3rd level slots it will go better for the dragon, of course. But it's definitely dead in the 2nd turn of combat at the very latest. On average rolls with average characters and a single critical hit, it's very, very likely to go down on turn 1.
That's 80 damage across 4 characters, so figure 100 for 5, and the dragon dies somewhere during round 2, which is what I said (magic weapons will boost things slightly, but probably not by 33). All of this assumes that the PCs have a clear line of fire on the dragon and can fire at will, which is not guaranteed (remember a white dragon has a Burrow speed).
Now, this ignores the dragon attacking. The fighter has 44 hp and Con save +5, the cleric and rogue are at 38 and +2, the wizard is at 32 and +2 (but likely has absorb elements), so if the dragon can breathe on two PCs (how likely this is depends on the lair layout) it's probably going to one-shot one of them. That's going to immediately reducing the party's damage output. That probably won't cause the encounter to go past 2 rounds unless the dragon gets lucky on initiative there's something additional going on (if the dragon was relaxing buried in a snow bank and makes a stealth check, which isn't super likely but certainly could happen, things could go really badly for the PCs; contrariwise if you assume the dragon isn't paying attention at all and lets the PCs prebuff with Aid, Bless, etc, one round becomes reasonable).
If you want an interesting encounter, you'll either need to substantially buff the dragon or give it a beneficial environment, but unless you play monsters as "it takes a pose to to let you conveniently shoot at it", it's not that trivial.
Incidentally, the problem with monster hp is really that PCs do too much damage. A typical front-loaded monster does something like 50% of hit points on round 1, 25% on round 2-3, with enough miss chance that it takes around 5 rounds to beat itself. If PCs were held to the same standards, they'd be doing something like 10 damage per PC on round 1, and 5 in subsequent rounds.
I liked your breakdown, and I think it's pretty accurate.
The dragon may one shot one of the PC's with its breath weapon, for sure. It needs to target those that have not taken a turn yet to have a significant impact and almost certainly still goes down turn 2 regardless as you say. This is also considering the party we've used as examples has no magical items, and everything has been done as a ranged attack (assuming the dragon is flying), the PCs don't attempt to surprise the dragon, and so on.
Re: hit points... it can't be said that the problem is the PC's doing too much damage, because monster hit points only have relevance in terms of how much damage they can take from the PCs, so the monster hp needs to be in line with expected damage outputs, not the other way around. The devs have tried to get around this by front-loading damage as you say, which means that fights typically end in 2-3 turns of combat. Personally I think this makes for unsatisfying encounters, and the whole random recharge of breath weapons and the like lends itself to potential TPKs if the dragon recharges on turn 2 and turn 3 (1 in 9 chance).
It also doesn't factor in that PCs aren't meant to have everything available and the daft 6-8 encounters idea, which only works if your entire game is nothing but dungeon crawls. I have some sympathy for the devs in trying to balance these things out, since you just can't know what level the party is, how many characters, how many NPC supports, how rested the party is and so on but the monsters are designed in a way that doesn't work for epic combats. It's a brief burst of cooldown ability popping and the BBEG is done in 12 seconds.
I dunno why I complain about this, I homebrew 90% of my monsters anyway /shrug
I would say, if these are children playing, then make sure the cleric has the components required for a resurrection spell, it isn't detailed anywhere in the adventure i am pretty sure but I made sure that my party found diamonds, enough to give the cleric 2 casts of revivify, and out of game (because they where all new) I mentioned to the cleric they might want to have a look at spell components before the party just cashed in on things they had found.
I also put a higher level priest in the town who was available to cast a higher level resurrection spell just in case, this would have required a bit of adventuring after to do some things to help this priest out, but it just means that a bad dice roll wont auto kill a character with no chance of getting them back.
The big reason PC damage is a problem is because the NPC party is something most DMs like to use at some point, and NPCs should at least be a semi-convincing emulation of PCs. This puts constraints on how tough you can reasonably make them. However, if you just put a party of PCs up against their perfect clones (which is by definition a coin-flip fight, way beyond deadly, and thus should take longer than a standard fight -- probably 4-5 rounds) you're going to have multiple characters down by the end of the first round. If PCs had an offense to hp ratio more like monsters, a 3 round fight would in fact be an "everyone is drained but probably not dead" fight.
An interesting thing to try might be an "Everyone and everything has max hp". It doesn't really change the overall difficulty of fights, but it makes it more practical to have an ordinary fight (drains resources and damages PCs, but the PCs are going to reliably win) last three rounds, and a super scary fight last four to five.