During the self-same trial, the evil clone of Gale doesn't follow the same rules as the rest of the game does: when he is invisible, he is also invincible -- even if I knew exactly where he is, no AoE-spell or anything can touch him. When invisible, he also does not care about any harmful surfaces and can just literally stand on them with no worry, whatsoever. What's more, he appears to have an infinite number of spell slots, since he just keeps spamming the hardest-hitting AoE-spell he has every round, whereas the original Gale can only cast it a couple of times before running out.
I'm not entirely certain if this is intended or not, but given how it completely breaks all the rules the rest of the game follows, it definitely feels like it's not intended or at least it shouldn't be.