Hi everyone, Im currently making a one shot for some friends who play with me weekly and adding a new player into the mix after I show her the basics of Dnd 5e. Fizban's released the Elder Brain Dragon and I wanted to use it a for the main BBEG. However, Im a tiny bit scared that when I put it to play that it would a blood bath for my Players. 

So if anyone out there could help me by giving me an answer that would greatly appreciated. 
I will also be giving my Players: 1 Very Rare , 2 rare and 4 Common Magic Items. 

Thank you again for your time and have a great day!

I would say that my biggest concern there is the combination of 'new player', '14th level' and 'one-shot'. 14th level characters can be quite complex, learning curve for figuring out exactly what you're doing probably exceeds the duration of a one-shot for even an experienced player let alone a new one.

On the dragon: CR 22 for a 14th level party isn't a big deal, and it's a one-shot, nothing wrong with a TPK as long as it's fun.

For the new player, I plan on helping her understand what each class can do and help her find her way into dnd. Give a east one or two quick hour long session or something alike that.

But thanks for the help on what to do next man.  

For what it's worth, sorry that the prior post didn't answer the question you wanted to answer.

Elder Brain Dragon has a lot of unique things to it compared to normal dragons.  High resistance to all forms of spellcasting except Dex(most other dragons have their one bad save as Int)  Blindsight to 120, which basically means forms of invisibility are done.  More dragons are 60.  The normal attack action has an automatic grapple on hit via the tail which can be used as a legendary action.  4 legendary resistances compared to 3.  Breath weapon is psychic which isn't very highly resisted AND has lingering damage effects, which would trigger concentration checks.  One of its legendary actions is it can automatically remove concentration from something.  

I haven't had the chance to run one yet, but they are definitely scary and since its a very different dragon I can see groups having issues.  Having its breath as a line and not a cone is the only saving grace it has as a stat block.

Space is scary, and so is this dragon.

Honestly, whenever I see a question like this, with a DM concerned about using X or running Y, my automatic answer is "then don't do it". You know your group, you know how you run your games, if you have concerns then there's likely a good reason for that. And we don't know anything about your group or you, so we're in not really in any position to offer valid insights.

Quote from pangurjan >>

Honestly, whenever I see a question like this, with a DM concerned about using X or running Y, my automatic answer is "then don't do it". You know your group, you know how you run your games, if you have concerns then there's likely a good reason for that. And we don't know anything about your group or you, so we're in not really in any position to offer valid insights.

.....what?

No.

What's wrong are knee-jerk reactions like this.  We can absolutely offer insight, don't just presume things and step beyond what the OP is asking.  Just answer the question and move on.  I don't need to assume anything about their table, etc.  In this case, talk about the merits of the Elder Brain and how you could see things happening.  There's more than enough information to give some surface level assessments. You know what level, magic item allocation, and the fact that it's a one shot.  So it's not meant to be taken serious, its just meant to be a one shot.  This won't be a 60 post discussion thread, it's going to be about 10 people or less giving advice, the OP will go hey thanks, and we'll move on.  

That's a perfectly good thread.  OP gets the advice they wanted, and can take it(or ignore it) as they want.

Really, unless the PCs are very poorly optimized, burn through their resources without stopping to rest before the fight, or otherwise do something horrible to shoot themselves in the foot I don't see an Elder Brain Dragon being overly dangerous for level 14 party.

why was i tagged

you werent, you just follow me and you see posts made me. Also, you weren't supposed to find this

Lmao was that one of the players lol

First, I had not noticed this vile thing before.  Oh my god, it is the stuff of nightmares on so many levels.

Second, do not send a newbie player against this thing, no matter what.   Ease them into the game first.   Give them some foreplay.  Then smack them upside the dice with this horror.

Third, it is hard to guess if your players can handle this thing.  If they are min-maxed up the wazoo, they should be able to handle it.   A 14th level sorlock with repelling blast could keep it away.  A druid with Anti-life shell is basically immune to everything your Elder brain dragon can do.    A paladin should be able to smite it to death, especially if they are Glory or Watcher.  

But if they spent more time on roleplaying than picking the most survivable character, this can kill them.  If they decided to be a 7 Wizard (Conjuration) / 7 Cleric of Arcana, because that sounded cool, etc. then they will get killed.

My dm is throwing one at a party of 8th levels

You can throw a powerful monster that you dont think they can defeat at a party and simply make it so they don't have to defeat it.  Especially in a one shot it's a good way to show it's not always kill or be killed.

Heck you can throw the tarrasque in the back ground of a fist fight  between unarmed naked level 1's as the city collapses around them. Cr only matters if you expect them to go for the kill. 

Not me planning to throw this at a 9th level party.

For fairness though, they have an army and the Authority at their side, so they should be fine. I hope

Funny enough, i'm actually about to do this to my level 9 party in a One-shot as the BBEG. My plan plane-shifting the Dragon as its about to die or a TPK when they will all be saved no matter what to give a possibility to start a campaing after de one-shot. I'll update on this :D

I think one of the nice things about running one-shots is the fact that you don't have to put as much effort into making sure that the game ends in a way that needs to continue into another session next week. If everyone gets turned into mindflayers at the end, hey, that's just a wild one-shot.

That said, I think the fact that you have a new player in this group is the only reason I think you should try to go for a simpler monster to cap off this one-shot. I think as long-time players it's easy to forget just how many rules there are in the game, and how many abilities a PC gets by 14th level. Just building a 14th level character sheet can be a pretty big time sink. I think a simpler boss monster with less absolutely dire effects would be better... a little buffer room for the new player to ease into the game.

Alternatively... you could just nerf the Elder Brain Dragon a bit. Even just reducing the DC of their breath weapon (which is really the biggest challenge that might frustrate or confuse a new player) would do a lot to make it a striking, but still beginner-friendly one-shot boss.