Actually changing my idea because I had something better!

Persona: Leviathan
Personality: created from the “Hermit” Arcana, Leviathan represents living a life in solid tide akin to the bottom of the ocean. However, this solitude was not without its benefits as Leviathan has come to be revered as the master of the Deep. When “awakened” the Leviathan whips up storms to empower its wielder.

Ultimate Form: Jormungandr the World Serpent. The biggest creature to prowl the oceans, and one day fated to swallow the world whole. 

(In addition, Jormungandr is said to be constantly “asleep” due to its fated prophecy to destroy the world when it wakes during Ragnarok, so the awakening would be a cool double meaning in this case)