Change new boss (HARD MODE)

[Mélusine]

In my opinion the boss is in a good state right now, even without bunny you can clear it on hard without much of problem other than the black goo on the floor mess up your dash some time.

But in the future if we really want abyss to become a harder boss, we can just take a page from MMORPG game and make a harder difficulty like heroic and give them less vision in the area.