so i think its come down to it all. malistare the undying is extremely hard and young morganthe is pretty hardcore. But..who's harder in your opinion.
malistaire the undying~ that universal immunity just kills me.
(oh, mally~ i'm the only person on this forum who doesn't hate your face, after what you did to me. why must you hurt me so?)
as for morganthe, she's easy as long as you don't trigger her cheats. i've fought her twice and while the random mammoths were really aggravating, they were mostly just inconvenient and it was easy to chip away at her with low-pip spells. my balance wizard only got mana-burned once, and it was because she fizzled; my death had a horrible time (since placing converts would have triggered some crazy cheat), so he spammed low-rank life treasure cards.. having an ice friend with him was very helpful as well.
Yeah, I feel like at some point they tossed young Morganthe a nerf.. apparently I wasn't here for it. But my ice is my highest level char and I remember surviving about 8 mammoths before I crashed when fighting her. (And I had a full team) Unluckily the pips number landed on me haha.