Merlin? Are you talking about the mage who was my teacher, but then left Cath Palug in my care before departing saying only, "Sorry, he's in your hands now!" THAT Merlin?
Hm? I guess he's different here.
Either way, I told him I was going to take his head next time I saw him.
I've already devised magecraft capable of dealing with an immortal incubus. I figure I have no other option but to make him experience death once so that he may turn over a new leaf.

Fate/Grand Order
Altria Caster
Dialogue 4 voice line