Pluton is a modified Brute designed to counter the strength of the Spartans. He probably served as the main antagonist of the Halo Legends episode: Odd One Out.
He was sent by the High Prophet of Truth to the planet Cronky with the objective of killing John 117 but ends up fighting SPARTAN-1337 instead. After some chaos and destruction, Mama opens a slipspace portal and fires a MAC Round at Pluton which results in drifting the beast to the Halo ring.
Covenant Sangheili: Ardo 'Moretumee | Bako 'Ikaporamee | Gek 'Lhar | Harka | Jul Mdama | Lat 'Ravamee | Luro 'Taralumee | Merg Vol | Ontomee | Re'gish Wamik | Rho 'Barutamee | Ripa 'Moramee | Rtas Vadum | Thel 'Vadam