Thetis

Thetis (テティス) is a character from Mega Man ZX Advent. He is a kind boy that loves swimming and the sealife, but he wants to punish and rid people from the world for dumping their waste into the sea. He is the chosen one for Model L, the Ice Mega Man. The player battles him at the Highway.

Model L grants Thetis many superhuman abilities, such as swimming at super speed, Ice manipulation, and the ability to breathe underwater.

Appearance
Thetis appears as a young boy with short blue hair styled into the infamous "ahoge" (literally translating to 'stupid hair'). He is characterized by his innocent, vibrant expression. He wears his Mega Men jacket right under his Mega Men-inspired hoodie and also sports a pair of shorts.

Personality
He's a kind person who appears to be quite upstanding. He loves the ocean and sealife. Beneath this exterior is an extremist however. He harbors animosity and hatred against mankind, participating in the Game of Destiny in order to gain the power to kill all humans and restore the earth to its pure state.

Mega Man ZX Advent
The player encounters him at the Arctic Ice Floe with Atlas. Instead of fighting you, he flees leaving you to fight Chronoforce.

The player encounters him again at the Highway where he is attacking citizens to feed Model W. He Megamerges and jumps into the ocean with Grey/Ashe following him. He explains that he is participating in the Game of Destiny to punish humans for polluting the sea. After he is defeated, he retreats and takes the Model W with him. He appears briefly after Grey/Ashe breaks Aeolus's cipher with all the other Mega Men.

He also appears after the defeat of the eight Pseudoroids in Ouroborous with Atlas, Aeolus, and Siarnaq. They are about to attack Grey/Ashe when Vent/Aile arrive and fights them instead, allowing the player to continue. After defeat of Albert, Ouroborous starts collapsing. Model Z seperates from Vent/Aile in order to keep Thetis and the other Mega Men busy by freezing the Biometals, which in turn freezes the four Mega Men. Their fates are unknown, but if the game is cleared in Hard Mode, all the Mega Men are seen 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 thinks happened to the original immortal Reploid data, the four showed up).

Attacks
When you fight him, you're in the ocean, reminiscent of Leviathan's battlefield in the Mega Man Zero series. He dash-swims in the screen, attacks and then swim-dashes out of the screen, sometimes even feinting his attack. When stopping, he twirls the Halberd around and fires off a triangular wave of energy not unlike Childre Inarabitta. His charged attack differs on who you are fighting him as. As Grey, he fires off a pair of ice dragons that home in on you. As Ashe, he manifests a thick, spiky ice formation which he then shatters, releasing a series of ice shards. These attacks can be countered using a fire attack or the Homing Lasers.

His ultimate attack involves him summoning a machine from underground that shoots out several snowflakes and then proceeds to create a vacuum that sucks in all nearby, the snowflakes themselves been dispersed about from the force. They can be destroyed before the vacuum effect occurs using Homing Lasers.

Etymology

 * Tethys was the name given to an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.
 * The name Thetis could be in reference to a sea nymph/sea-goddess found in Greek mythology or possibly even Tethys who may have been a primordial deity of Archaic Greece as a Titaness and aquatic sea goddess.

Trivia

 * Thetis appears to be the only Mega Man in ZX Advent who wishes to think about peace. This is also shown in his line after your battle with him, "I thought you of all people would understand me.", and may indicate that his is actually a good character, but his was corrupted by model W. He is also the only enemy that appears to want to appeal to the player, with all other enemies indicating annoyance at their "failure to understand" or feeling that nobody else would "understand the glory of our plans".
 * For unknown reasons, Grey refers to Thetis as being human even though he is supposed to be a Reploid.