So. The Heliophage. The final mission of the game. Climatic confrontation with Rendain on Tempest. Timed first part with lots and lots of powerful enemies. A difficult final boss who summons other bosses from the past missions to fight you. All in all, that’s why the Heliophage is : a badass final mission for a badass game whit badass players who play badass characters.
…Or not.
Because of two little, teensy mechanics, the mission becomes almost undoable when trying anything else than solo mode : I’m talking about the combination of the knocknack mechanics coupled with the whole “arena without ledges suspended over the Void” thing.
Every ■■■■■■■ attack of Rendain in the second phase either has for goal to knock you into an insta-kill fall, or to stun you for proceeding with said attack who knocks you into the fall, OR to summon more thralls than in the whole first part of the mission who will either knock you into the Void or distract you long enough for Rendain to knock you into the Void AGAIN.
Now, I get it : it’s the final boss. It’s supposed to be hard. I know this. But there is a difference between hard and “so unfair you throw your controller at your screen”. No matter how you’re built, no matter how skilled your team is, no matter how much time you spend in the mission, no matter how hard you want that last Silver rank to unlock Kleese (my case, BTW), Rendain will throw all of this alongside your miserable corpse into the Void.
This isn’t hard. It’s unfair : No other boss in the campaign are that unfair. You could buff Rendain’s damage and change the arena, and the boss fight would still be difficult, without being unfair.
Don’t get me wrong : you can win it. I did once. People did it too, or else I would see absolutely no Deande or Ghalt in multiplayer. But godamnit, I don’t want to spend 45 minutes of my life only for my team to lose 8 lives in three minutes after clearing everything else in the mission.
Devs, if you see this, I only ask of you this : Please, please, please, PLEASE, either change the arena, Reece the number of thralls summoned, reduce the knockback on the bosses attacks in this mission, or a mix of the three. I love this game, and it really sucks to lose the final boss fight in such a sad, laughable manner.

(Though this can be ignored if you just want to get the mission done)