Demon Gate

[Raistlin]

I think the only thing about the Materia Keeper that I found difficult was both waiting for Trine to be cast and not accidentally killing him before that,

Haha, yes. I always tried to get Trine here, and the waiting could get annoying.

or the times I forget he's immune to Fire and I bring in my newly acquired Vincent and activate his first Limit Break form...

I rarely used Vincent after my first playthrough, but that would be pretty funny.