I'm looking to balance an encounter for a final boss where the main party will go through the day encountering their own monsters but right before the final creature, cr30, they are joined by a level 20 sorcerer. Would the sorcerer make the encounter easier as they have not been fighting throughout the day and haven't used health/spell slots or would it calculate out at the same difficulty?
The short answer is, yes, adding an ally to the party will make the encounter easier. Whether or not you need to rebalance the encounter is impossible to say. It’s going to depend on how many resources the party needs to use on their way to the fight, and a ton of other factors, like lair actions and terrain in general, what kinds of things the party has access to compared to what the monster can do. CR is an imperfect measure. It can get you in the ballpark, but in the end you’ll need to go with your gut.
The thing that makes this extra tricky is the fact that the PCs will have been fighting all day and will have “used” a significant amount of their daily budget, but obviously the Sorcerer has not. This gets into a fairly complicated figuring about daily XP budgets.
I'm looking to balance an encounter for a final boss where the main party will go through the day encountering their own monsters but right before the final creature, cr30, they are joined by a level 20 sorcerer. Would the sorcerer make the encounter easier as they have not been fighting throughout the day and haven't used health/spell slots or would it calculate out at the same difficulty?
The short answer is, yes, adding an ally to the party will make the encounter easier.
Whether or not you need to rebalance the encounter is impossible to say. It’s going to depend on how many resources the party needs to use on their way to the fight, and a ton of other factors, like lair actions and terrain in general, what kinds of things the party has access to compared to what the monster can do. CR is an imperfect measure. It can get you in the ballpark, but in the end you’ll need to go with your gut.
The thing that makes this extra tricky is the fact that the PCs will have been fighting all day and will have “used” a significant amount of their daily budget, but obviously the Sorcerer has not. This gets into a fairly complicated figuring about daily XP budgets.
https://www.dndbeyond.com/sources/dmg/creating-adventures#CreatingEncounters
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