For example, the AOE (area of effect) spell "Cloudkill":
When a creature enters the spell’s area for the first time on a turn or starts its turn there, that creature must make a Constitution saving throw. The creature takes 5d8 poison damage on a failed save, or half as much damage on a successful one. Creatures are affected even if they hold their breath or don’t need to breathe.
Say you cast this in a 15×15 room. It should cover the entire room, and as such, the question remains – are you affected by the cloud, as well as the enemies?
I'd hazard a guess as yes, as it doesn't specify "other than you," but I just want to make sure so I don't cast it and TPK by accident.
Best Answer
Yes, a caster is affected by their own AOE unless the spell or ability states otherwise
Cloudkill says:
The caster is "a creature" certainly, so, barring anything in the spell that says otherwise, they are affected.
Certain spells/abilities allow you to choose your targets. The best example is probably the Evocation School Wizard class ability sculpt spells which allows the wizard to choose creatures (including themself) to not be affected when they are in the range of evocation spells that they use.
Don't walk into your own AOEs folks.