Thetis

Thetis is a kind boy that loves swimming and the sealife, but he wants to punish and rid people for dumping waste into the sea. He is the chosen one for model L, the Ice Mega Man. The player battles him at the Highway.

Personality
She's a kind person who appears to be an upstanding person. She loves the ocean and sealife. However She has a nasty side as well. She hates humans for polluting the sea and plays the Game of Destiny to punish them.

Megaman ZX Advent
You encounter him at the arctic Ice Floe with Atlas. Instead of fighting you, he flees leaving you to fight Chronoforce.

You encounter him again at the Highway where he is attacking citizens to feed Model W. He Megamerges and jumps into the ocean with you following him. He explains that he is participating in the Game of Destiny to punish human for polluting the sea. Then you battle him and defeat him. He retreats and takes the Model W with him. He appears briefly after you break Aeolus's cipher with all the other Megamen. He also appears after you defeat the 8 Psuedoroids in Ouroborous with Atlas, Aeolus, and Siarnaq. They are about to attack you when Vent/Aile arrive and fights them instead, allowing you to continue. After you defeat Albert, Ouroborous starts collapsing. Model Z seperates from Vent/Aile in order to keep Thetis and the other Mega Men busy. Model Z freezes their Biometal which freezes them. Their fates are unknown but if you clear the game in Hard mode, you can see all the Mega Men well and alive in their megamerged forms. (It's also implied that the original immortal Reploid Data was inserted into them, as, right after Master Thomas asked Master Mikhail what he think happened to the original immortal Reploid data, they showed up).

Attacks
When you fight him, you're in the ocean, reminiscent of Leviathan's battlefield in the Zero Series. He dash-swims in the screen, attacks and then swim-dashes out of the screen. He sometimes uses the spinning halberd attack or the triangular ice projectile. If you're Grey, he'll fires an ice dragons like Leviathan's. If you're Ashe, he'll create a chunk of ice and shatter it, causing the fragments to fly in differnt directions. He will also summon Ice flower cannon to fires some current at you. Then he will create a tornados of snowflakes, also like Leviathan except that snowflakes is homing spears.