I have a group of players who do not know (yet) how to get rid of a Flameskull.
They already destroyed it twice. The second time there were right next to it when it re-materialized and they had enough fire power to destroy it on the first round (they got lucky!)
Now, I'm wondering, can the Flameskull remember who destroyed it before?
I am thinking that, if the answer is yes, then it should use Fireball on the very first round, no hesitation... (even if it is itself inside) since it knows that otherwise it is more than likely to get destroyed without a chance to kill any of its opponents.
So I could imagine a Lich and a Mummy Lord as having quite a bit of memory, but I'm not so sure about the Flameskull...