The final boss is a behemoth from the depths, its massive body a swirling storm of blackness. You'll need all your wits and reflexes to take it down.
This attack involves a combination of Abyssal Frenzy and Abyssal Frenzy 2: Electric Boogaloo to create an unstoppable force of nature.
Use The Dark Reflection to redirect the attack, but be warned: it's just a temporary solution - the Abyss won't stay hidden for long.