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Tretista Kelverian (トレテスタ・ケルベリアン Toretesuta Keruberian) is one of the bosses in Mega Man Zero 3. Tretista is based on Cerberus, the three headed hellhound. He is one of the Eight Gentle Judges, and has three independent thought circuits that he uses to reach a fair judgement. These circuits act as the voices of compassion, aggression, and reason. When Dr. Weil brainwashed him to be one of Weil's Numbers, he could not think properly. Instead, his aggressive traits were amplified, furthering his beast-like nature, and he became violent and arrogant. When Zero went to investigate a giant elevator created by Neo Arcadia, he finds Kelverian protecting it, fighting him. Zero then discovers the elevator is used to transport mass amounts of E-Crystals to be used as energy. As with the other Judges, Kelverian reappears in the final stage, but is defeated again by Zero.


Tretista attacks by separating the dogs attached to his shoulders, which then jump around the room, throwing a box and then dashing to destroy it, spitting vaporous energy balls across the floor, and bending a metal bar into a V shape and then tossing it like a boomerang. At A or S rank he will use his EX attack, where a large laser occasionally comes from his claw when he dashes to the box.

Defeating him gives Zero the Absorber Body chip and, if at A or S rank, the Gale Attack ability.


Nickname: Rabid Dog Protection (咬哭の守護 Koukoku no Shugo)
EX Skill: Laser Claw (レーザークロウ)
Tretista Kelverian drops a large crate on the ground, then generates a large, purple energy laser, in the form of a blade from his claw, and rushes forward to destroy it.

Mission: Search Facility
Zero's EX Skill: Gale Attack (Reppuugeki)

Stage enemies

Enemies in Tretista Kelverian's stage.



  • Tretesta (Tretista) comes from Italian tre (three) and testa (head); also, tritesta is Italian for three-headed, while Keruberian (Kelverian) is a play of Kerberos (ケルベロス Keruberosu; also known as Cerberus in English). Therefore, his name means "Three-Headed Kerberos".
  • In the English-localized Mega Man Zero 3 instruction manual, Tretista is better translitterated as "Tretesta Kerberion".
  • Tretista breaks the tradition of having two life bars as one of the eight main bosses in the Mega Man Zero series, having a third bar and surpassing the other judges' health.
  • Tretista and Childre Inarabitta are the only members of the Weil's Numbers that first appear to Zero already morphed in their Punishment forms. He only assumed his humanoid form briefly during the final stage, morphing afterwards.
  • Coincidentally, Tretista's appearance is similar to that of Omega's second form, in that they both have heads attached to their shoulders instead of closer to the middle head.
  • The boss Bifrost the Crocoroid from Mega Man ZX Advent has an appearance that is quite similar to that of Tretista. Both have similar standing animations, and both have an attack that sends a rolling weapon across the floor.
  • His three heads having a different thought system for judgement could be a reference to the three judges of Hades Rhadamanthys, Eacus, and Minos.
  • If Tretista manages to drop one his crates on Zero at a corner, it is an instant kill regardless of Zero's vitality.