Verminion

[StouterTaru]

They manage to destroy everyone even with a minion in them.

There's 2 different, similar looking attacks. Early on he just uses an AoE attack that will kill just about everyone inside it, so move out. Then he adds the tower attack, which will only damage anyone inside it, unless nobody is inside it, then it destroys everyone. The fight requires constant micromanaging. You can't swarm him, or else he will run to the next arcana stone. Just attack with 4 Cid/Gentlemen at a time, and have some more on reserve.