Hello! I'm a DM running Dragon of icespire peak, and the characters are on level 5. And I realized something. Fighter+2 paladins+evoker+bard with Dragon slayer vs a young white Dragon. This won't be much of a boss battle, and more of an all-out beat down. A party of 5 level 6 characters will thrash,bash, and crash cryovain. How do I make this a fair fight?
Rollback Post to RevisionRollBack
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
Keep movement speeds in mind. It can fly and hover. There’s no reason for it to land. Then the Pallys can’t melee, so they can’t smite. Unless fighter is ranged, they’ll be at a disadvantage, too, plinking away with that longbow they got back at 1st level and haven’t used since. The dragon can hang out up high and wait for it’s breath to recharge. White dragons also have a burrow speed. If it’s underground, casters can’t see it to target it. And burrow doesn’t have to mean ground. It could dive into cavern walls or even ceilings. And if that’s not enough, give it some lair actions that an adult dragon would have.
I agree about Cryovain being easy. Especially if you consider the necklace of fireballs and dragon slayer sword! I agree about lair actions and flying around. Do not follow the module and have him napping when the players arrive- they will crush him with a surprise round.
You can also buff his hit points or fudge breath weapon recharge rolls.
Make sure he plays smart. When I was a player Cryovain flew back to the lower floor. My rogue ran down the stairs to chase him and he nearly killed her with a readied attack. Things like that will make the fight seem closer to the players.
Add some talking in combat, dramatic wording- even if it seems easy, make it sound epic.
Keep movement speeds in mind. It can fly and hover. There’s no reason for it to land. Then the Pallys can’t melee, so they can’t smite. Unless fighter is ranged, they’ll be at a disadvantage, too, plinking away with that longbow they got back at 1st level and haven’t used since. The dragon can hang out up high and wait for it’s breath to recharge. White dragons also have a burrow speed. If it’s underground, casters can’t see it to target it. And burrow doesn’t have to mean ground. It could dive into cavern walls or even ceilings. And if that’s not enough, give it some lair actions that an adult dragon would have.
I think you have a point. But the players would find fighting a flying Dragon a little boring if you know what I mean. The lair actions are good though so I might use them.
Rollback Post to RevisionRollBack
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
Hello! I'm a DM running Dragon of icespire peak, and the characters are on level 5. And I realized something. Fighter+2 paladins+evoker+bard with Dragon slayer vs a young white Dragon. This won't be much of a boss battle, and more of an all-out beat down. A party of 5 level 6 characters will thrash,bash, and crash cryovain. How do I make this a fair fight?
Is it actually supposed to be an epic boss battle? If so, either upgrade to an adult or throw in a fake of some sort (Cryovain isn't actually the BBEG, someone or something is manipulating him).
Hello! I'm a DM running Dragon of icespire peak, and the characters are on level 5. And I realized something. Fighter+2 paladins+evoker+bard with Dragon slayer vs a young white Dragon. This won't be much of a boss battle, and more of an all-out beat down. A party of 5 level 6 characters will thrash,bash, and crash cryovain. How do I make this a fair fight?
Is it actually supposed to be an epic boss battle? If so, either upgrade to an adult or throw in a fake of some sort (Cryovain isn't actually the BBEG, someone or something is manipulating him).
It’s sort of an introductory campaign. Perhaps he’s supposed to be easy at higher level to make sure the players win and feel good about how well they did. Especially since his presence is felt the whole campaign, and the entire goal is to get enough power to defeat him. ‘We killed the dragon that nearly killed us at first level!’
Well I reckon the thing is that the dragon of icespire peak isn't always gonna be 4 or 5 players. So if there is 2 players, Dragon slayer would be needed. Now the cryovain fight may not be intended as an epic boss fight, but I feel the players will enjoy an epic boss battle to end the campaign. But the whole thing is not over, because I plan to play the beyond the dragon of icespire peak trilogy (storm lords wrath, sleeping dragons wake, divine contention) an adult white Dragon would surely overwhelm the players, so thats a no no. I could homebrew a cryovain stat block, or even better: a teen white Dragon stat block.
Rollback Post to RevisionRollBack
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
Keep movement speeds in mind. It can fly and hover. There’s no reason for it to land. Then the Pallys can’t melee, so they can’t smite. Unless fighter is ranged, they’ll be at a disadvantage, too, plinking away with that longbow they got back at 1st level and haven’t used since. The dragon can hang out up high and wait for it’s breath to recharge. White dragons also have a burrow speed. If it’s underground, casters can’t see it to target it. And burrow doesn’t have to mean ground. It could dive into cavern walls or even ceilings. And if that’s not enough, give it some lair actions that an adult dragon would have.
I think you have a point. But the players would find fighting a flying Dragon a little boring if you know what I mean. The lair actions are good though so I might use them.
Make them think of a way to make it land. Or just have it up for a couple rounds let it breath once or twice, to soften them up, then say it gets a look of smug overconfidence and land to start melee. And since at that point, the wizard or bard has been doing the damage, it would focus on them. And there’s always the old, fly in, grapple someone, fly back up and drop them. And if it lands and things are going poorly, that’s when it burrows. I think moving around is really going to be key. If it just stands there trying to slug it out, the PCs will win easily. But if it keeps moving around, it gets harder. Another choice could be re-skinning a different dragon, like a green or a red or something, just pick one that’s a slightly higher cr, and change it’s breath weapon to cold.
Do not forget the lair actions or the environment. That whole area is difficult terrain. One of the lair actions is to put up an ice wall. I used it to push melee characters away and jump to the rear ranged attackers.
I also put ice walls at the entrance and sides to ensure that there would be no surprise round (as mentioned by a previous post). Their actions are to break the wall and alert the dragon. They rush out onto the roof. If you position correctly, you can get every one of them on the initial breath weapon. I did drop the cleric with a failed con save.
Thanks for all the replies! I have homebrewed a cryovain stat block but can't share it because its too similar to adult white dragons. It's basically a creature which has lair actions but no legendary ones, AC 17, one more hit dice than cryovain, its huge so those hit dice are d12s, and it's str and con have gone from 18 to 20, and the breath weapon save DC is increased due to con adjustments and proficiency bonus increases, and there is one more d8 in the damage of cryovains breath weapon.
Rollback Post to RevisionRollBack
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
I swapped it to a young blue dragon when I ran it and tied the dragon into the Priests of Talos storm cult plot lines. This was suggested somewhere on the internet to try to make the overall DoIP plot a bit more integrated and I found it worked well.
Also, playing the dragon intelligently also helps. Does the dragon know that the party is in the building and on their way? Does the dragon hear or see them? These will affect its tactics. The dragon might perch on top of the building at the top of the castle where the characters can't see or hit them unless they come outside. The dragon can fly, use their breath weapon (then wait for it to recharge), grapple a character and drop them over the castle parapet ... lots of very dangerous tactics it can make use of.
One other thing you might need to do is to put a dragon treasure hoard at the castle on the roof or somewhere the characters need to go through the dragon to get to. If I recall, there wasn't much in the way of treasure and no magic items in the final encounter which I found remarkable (the dragon seems to have no treasure and no investment in the location). If the dragon doesn't have treasure at the castle why would they stick around to fight? I think this is a major flaw with the plot at the end of DoIP. Young dragons aren't that bright but even they would know there is no point in fighting over a stone parapet when there is no treasure involved. So you may need to modify these scenes so they make a bit more sense.
I swapped it to a young blue dragon when I ran it and tied the dragon into the Priests of Talos storm cult plot lines. This was suggested somewhere on the internet to try to make the overall DoIP plot a bit more integrated and I found it worked well.
Also, playing the dragon intelligently also helps. Does the dragon know that the party is in the building and on their way? Does the dragon hear or see them? These will affect its tactics. The dragon might perch on top of the building at the top of the castle where the characters can't see or hit them unless they come outside. The dragon can fly, use their breath weapon (then wait for it to recharge), grapple a character and drop them over the castle parapet ... lots of very dangerous tactics it can make use of.
One other thing you might need to do is to put a dragon treasure hoard at the castle on the roof or somewhere the characters need to go through the dragon to get to. If I recall, there wasn't much in the way of treasure and no magic items in the final encounter which I found remarkable (the dragon seems to have no treasure and no investment in the location). If the dragon doesn't have treasure at the castle why would they stick around to fight? I think this is a major flaw with the plot at the end of DoIP. Young dragons aren't that bright but even they would know there is no point in fighting over a stone parapet when there is no treasure involved. So you may need to modify these scenes so they make a bit more sense.
Agreed. Plus PCs want treasure when they fight a dragon. I rolled up a hoard using the DM's guide.
I am using a Blue dragon as well, but if they already saw that it was white, you could say that the readon Cryovain wanted a new lair was because a) it is female and was readying to lay eggs, so there are white dragon wyrmlings with it or b) that it is male and his mate is ready to lay eggs so it was hunting for it, so there are actually two young white dragons.
Add some jokes about Cryovain doing their best as teenage parent for bonus points.
All these responses are really great! I'm gonna use the cryovain stat block I made though (basically with lair actions, he's huge, and he has better con and str, his breath weapon is a little bit better, and he has another hit die) but I reckon I'll give him a treasure hoard and do something about the stone-cold reavers(cause they are BORING).
Rollback Post to RevisionRollBack
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
All these responses are really great! I'm gonna use the cryovain stat block I made though (basically with lair actions, he's huge, and he has better con and str, his breath weapon is a little bit better, and he has another hit die) but I reckon I'll give him a treasure hoard and do something about the stone-cold reavers(cause they are BORING).
I had them working for an evil sorcerer that Cryovain drove away from the keep when he arrived. This sorcerer had to leave a very powerful magic item behind and the stone cold reavers have instructions to find it and retrieve it when the dragon is gone.
Halia Thornton may have been involved. :) (She is my favorite NPC in this campaign- sneaky, sort of evil, and also the only way for PCs to cash in their valuable items in town!)
He'll still go down on turn 1 of the combat if the party are fresh.
But his constitution is +5 now and his hit die are d12s instead of d10s, for a total of 161 avg. HP.
Rollback Post to RevisionRollBack
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
He'll still go down on turn 1 of the combat if the party are fresh.
But his constitution is +5 now and his hit die are d12s instead of d10s, for a total of 161 avg. HP.
It's better, but it's still weak and will be over in 2 turns. If your players know how to play, and are optimised, then:
To kill it in 1 turn, they need to deal 33 damage each. For a paladin using a 2nd level smite on an attack, let's assume that they hit for 1d8+4+3d8 = 22 per attack. With 2 attacks, they should each land one with average rolls. If they inflict a critical hit, they'll deal 40 on a single attack. But let's assume one hit each, so 22 damage per turn from the paladins.
The Evoker's most reliable spell is probably to cast magic missile at 3rd level, for 17 (5d4+5) guaranteed damage, but he could equally just toss a fireball for an average 28 on a failed save or 14 on a pass.
The Fighter will likely be hitting for around 9 (1d8+4) if not optimised, and up to 21 (2d6+14) if he is using GWM, and has 4 attacks on his first turn due to Action Surge.
Your dragon might get a 2nd turn in the combat, and is very unlikely to get to a third. That's fine if your players aren't really into combat much, but for a boss fight I'd aim to have them fighting a minimum of 4 turns. If you test the party with a bunch of encounters prior to this one, so they don't have spell slots, actions surge etc. then what you've got here is probably ok for that.
Don't worry about sticking to guidelines about constitution, hit dice etc. Just give it the hit points you want it to have. The players aren't ever going to know. Monsters don't follow the rules in general anyway. A good way to do this is to look at a character's damage if all their most powerful attacks hit, total it across all characters, halve that number, then multiply the result by the number of turns you want the fight to last.
E.g. average character damage is 30 per turn if they hit with everything. 5 characters = 150 damage. Halve it to 75. I want the fight to last 3 turns, so 3 turns x75 hp = 225 hit points.
Rollback Post to RevisionRollBack
To post a comment, please login or register a new account.
Hello! I'm a DM running Dragon of icespire peak, and the characters are on level 5. And I realized something. Fighter+2 paladins+evoker+bard with Dragon slayer vs a young white Dragon. This won't be much of a boss battle, and more of an all-out beat down. A party of 5 level 6 characters will thrash,bash, and crash cryovain. How do I make this a fair fight?
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
Keep movement speeds in mind. It can fly and hover. There’s no reason for it to land. Then the Pallys can’t melee, so they can’t smite. Unless fighter is ranged, they’ll be at a disadvantage, too, plinking away with that longbow they got back at 1st level and haven’t used since. The dragon can hang out up high and wait for it’s breath to recharge.
White dragons also have a burrow speed. If it’s underground, casters can’t see it to target it. And burrow doesn’t have to mean ground. It could dive into cavern walls or even ceilings.
And if that’s not enough, give it some lair actions that an adult dragon would have.
I agree about Cryovain being easy. Especially if you consider the necklace of fireballs and dragon slayer sword! I agree about lair actions and flying around. Do not follow the module and have him napping when the players arrive- they will crush him with a surprise round.
You can also buff his hit points or fudge breath weapon recharge rolls.
Make sure he plays smart. When I was a player Cryovain flew back to the lower floor. My rogue ran down the stairs to chase him and he nearly killed her with a readied attack. Things like that will make the fight seem closer to the players.
Add some talking in combat, dramatic wording- even if it seems easy, make it sound epic.
Only spilt the party if you see something shiny.
Ariendela Sneakerson, Half-elf Rogue (8); Harmony Wolfsbane, Tiefling Bard (10); Agnomally, Gnomish Sorcerer (3); Breeze, Tabaxi Monk (8); Grace, Dragonborn Barbarian (7); DM, Homebrew- The Sequestered Lands/Underwater Explorers; Candlekeep
Upgrade to adult white dragon?
I think you have a point. But the players would find fighting a flying Dragon a little boring if you know what I mean. The lair actions are good though so I might use them.
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
Is it actually supposed to be an epic boss battle? If so, either upgrade to an adult or throw in a fake of some sort (Cryovain isn't actually the BBEG, someone or something is manipulating him).
It’s sort of an introductory campaign. Perhaps he’s supposed to be easy at higher level to make sure the players win and feel good about how well they did. Especially since his presence is felt the whole campaign, and the entire goal is to get enough power to defeat him. ‘We killed the dragon that nearly killed us at first level!’
Only spilt the party if you see something shiny.
Ariendela Sneakerson, Half-elf Rogue (8); Harmony Wolfsbane, Tiefling Bard (10); Agnomally, Gnomish Sorcerer (3); Breeze, Tabaxi Monk (8); Grace, Dragonborn Barbarian (7); DM, Homebrew- The Sequestered Lands/Underwater Explorers; Candlekeep
Well I reckon the thing is that the dragon of icespire peak isn't always gonna be 4 or 5 players. So if there is 2 players, Dragon slayer would be needed. Now the cryovain fight may not be intended as an epic boss fight, but I feel the players will enjoy an epic boss battle to end the campaign. But the whole thing is not over, because I plan to play the beyond the dragon of icespire peak trilogy (storm lords wrath, sleeping dragons wake, divine contention) an adult white Dragon would surely overwhelm the players, so thats a no no. I could homebrew a cryovain stat block, or even better: a teen white Dragon stat block.
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
Make them think of a way to make it land. Or just have it up for a couple rounds let it breath once or twice, to soften them up, then say it gets a look of smug overconfidence and land to start melee. And since at that point, the wizard or bard has been doing the damage, it would focus on them.
And there’s always the old, fly in, grapple someone, fly back up and drop them.
And if it lands and things are going poorly, that’s when it burrows.
I think moving around is really going to be key. If it just stands there trying to slug it out, the PCs will win easily. But if it keeps moving around, it gets harder.
Another choice could be re-skinning a different dragon, like a green or a red or something, just pick one that’s a slightly higher cr, and change it’s breath weapon to cold.
Do not forget the lair actions or the environment. That whole area is difficult terrain. One of the lair actions is to put up an ice wall. I used it to push melee characters away and jump to the rear ranged attackers.
I also put ice walls at the entrance and sides to ensure that there would be no surprise round (as mentioned by a previous post). Their actions are to break the wall and alert the dragon. They rush out onto the roof. If you position correctly, you can get every one of them on the initial breath weapon. I did drop the cleric with a failed con save.
Thanks for all the replies! I have homebrewed a cryovain stat block but can't share it because its too similar to adult white dragons. It's basically a creature which has lair actions but no legendary ones, AC 17, one more hit dice than cryovain, its huge so those hit dice are d12s, and it's str and con have gone from 18 to 20, and the breath weapon save DC is increased due to con adjustments and proficiency bonus increases, and there is one more d8 in the damage of cryovains breath weapon.
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
I swapped it to a young blue dragon when I ran it and tied the dragon into the Priests of Talos storm cult plot lines. This was suggested somewhere on the internet to try to make the overall DoIP plot a bit more integrated and I found it worked well.
Also, playing the dragon intelligently also helps. Does the dragon know that the party is in the building and on their way? Does the dragon hear or see them? These will affect its tactics. The dragon might perch on top of the building at the top of the castle where the characters can't see or hit them unless they come outside. The dragon can fly, use their breath weapon (then wait for it to recharge), grapple a character and drop them over the castle parapet ... lots of very dangerous tactics it can make use of.
One other thing you might need to do is to put a dragon treasure hoard at the castle on the roof or somewhere the characters need to go through the dragon to get to. If I recall, there wasn't much in the way of treasure and no magic items in the final encounter which I found remarkable (the dragon seems to have no treasure and no investment in the location). If the dragon doesn't have treasure at the castle why would they stick around to fight? I think this is a major flaw with the plot at the end of DoIP. Young dragons aren't that bright but even they would know there is no point in fighting over a stone parapet when there is no treasure involved. So you may need to modify these scenes so they make a bit more sense.
Agreed. Plus PCs want treasure when they fight a dragon. I rolled up a hoard using the DM's guide.
Only spilt the party if you see something shiny.
Ariendela Sneakerson, Half-elf Rogue (8); Harmony Wolfsbane, Tiefling Bard (10); Agnomally, Gnomish Sorcerer (3); Breeze, Tabaxi Monk (8); Grace, Dragonborn Barbarian (7); DM, Homebrew- The Sequestered Lands/Underwater Explorers; Candlekeep
I am using a Blue dragon as well, but if they already saw that it was white, you could say that the readon Cryovain wanted a new lair was because a) it is female and was readying to lay eggs, so there are white dragon wyrmlings with it or b) that it is male and his mate is ready to lay eggs so it was hunting for it, so there are actually two young white dragons.
Add some jokes about Cryovain doing their best as teenage parent for bonus points.
Double its hit points. You'll be doing that for every boss monster from level 5 onwards. Standard monster hp are a bit of a joke for bosses.
All these responses are really great! I'm gonna use the cryovain stat block I made though (basically with lair actions, he's huge, and he has better con and str, his breath weapon is a little bit better, and he has another hit die) but I reckon I'll give him a treasure hoard and do something about the stone-cold reavers(cause they are BORING).
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
He'll still go down on turn 1 of the combat if the party are fresh.
I had them working for an evil sorcerer that Cryovain drove away from the keep when he arrived. This sorcerer had to leave a very powerful magic item behind and the stone cold reavers have instructions to find it and retrieve it when the dragon is gone.
Halia Thornton may have been involved. :) (She is my favorite NPC in this campaign- sneaky, sort of evil, and also the only way for PCs to cash in their valuable items in town!)
Only spilt the party if you see something shiny.
Ariendela Sneakerson, Half-elf Rogue (8); Harmony Wolfsbane, Tiefling Bard (10); Agnomally, Gnomish Sorcerer (3); Breeze, Tabaxi Monk (8); Grace, Dragonborn Barbarian (7); DM, Homebrew- The Sequestered Lands/Underwater Explorers; Candlekeep
But his constitution is +5 now and his hit die are d12s instead of d10s, for a total of 161 avg. HP.
When you thought you knew about spellcasting - you played a warlock
Why are most bard colleges a pain to type? I mean bard college of valor, compare to champion or evoker. Same goes for sacred oaths: paladin oath of devotion. That's even worse.
I don't think WoCE were very creative with the rogue and ranger subclass titles. I mean ranger archeotype? Roguish archeotype? Bro! Fighters are better but still is somewhat unsatisfying compare to a monastatic tradition or sacred oath.
It's better, but it's still weak and will be over in 2 turns. If your players know how to play, and are optimised, then:
To kill it in 1 turn, they need to deal 33 damage each. For a paladin using a 2nd level smite on an attack, let's assume that they hit for 1d8+4+3d8 = 22 per attack. With 2 attacks, they should each land one with average rolls. If they inflict a critical hit, they'll deal 40 on a single attack. But let's assume one hit each, so 22 damage per turn from the paladins.
The Evoker's most reliable spell is probably to cast magic missile at 3rd level, for 17 (5d4+5) guaranteed damage, but he could equally just toss a fireball for an average 28 on a failed save or 14 on a pass.
The Fighter will likely be hitting for around 9 (1d8+4) if not optimised, and up to 21 (2d6+14) if he is using GWM, and has 4 attacks on his first turn due to Action Surge.
Your dragon might get a 2nd turn in the combat, and is very unlikely to get to a third. That's fine if your players aren't really into combat much, but for a boss fight I'd aim to have them fighting a minimum of 4 turns. If you test the party with a bunch of encounters prior to this one, so they don't have spell slots, actions surge etc. then what you've got here is probably ok for that.
Don't worry about sticking to guidelines about constitution, hit dice etc. Just give it the hit points you want it to have. The players aren't ever going to know. Monsters don't follow the rules in general anyway. A good way to do this is to look at a character's damage if all their most powerful attacks hit, total it across all characters, halve that number, then multiply the result by the number of turns you want the fight to last.
E.g. average character damage is 30 per turn if they hit with everything. 5 characters = 150 damage. Halve it to 75. I want the fight to last 3 turns, so 3 turns x75 hp = 225 hit points.