Eh, is this a conjecture of an actual plan or a random talk? Because it certainly looks like the later.

And, anything that fire can do to anyone's cells, lightning and corrosives can as well. Just telling you. Either way, as long as this is fantasy, only things explicitly said to cut someone's regeneration will do so, kinda D&D-like style.

For this instance, this creature's regeneration can't be dealt with at all. You'll find why's that in the following main event. You can kill it, but it'll take a bit of work because of this.

A hard victory is more accomplishing, after all. Am I right?