Mephisto appeared in both Thanos' stage and Blackheart's ending.
His ending is the same generic one used by all other secret characters: he stands in front of a flashing blue background, his back turned to the screen while the text "Congratulations! You've defeated the game with a secret character!" appears underneath him.
Mephisto shares all of Blackheart's moves and Hyper Combos. His attacks set the enemy on fire when hit. Originally, he was been planned to be featured as a special move or hyper combo in Blackheart's moveset, with incomplete sprites being leftover in Marvel Super Heroes vs. Street Fighter ROMs. Judging from the sprites, this was meant to be an attack where Blackheart summons Mephisto to grab his opponent and breath hellfire upon them.
- Dark Thunder: Shoot bolts of energy towards the opponent. Light Version travels on the ground, Medium Version travels straight ahead, while the Hard Version shoots diagonally, an anti-air.
- Inferno: Summons a pit from the ground and shoots either ice, fire, or lightning upward. Light Punch creates the pit in front of you while the hard punch tracks the opponent.
- Armageddon: Mephisto summons a bunch of meteors to fall down. Must be in close range for the Hyper Combo to work at its best.
- Heart of Darkness: Mephisto attacks with energy blasts and gargoyles, then following up with a pit that shoots energy upwards.
- Judgment Day: (Can also be done in the air) Shoots a bunch of small demons at the opponent. On the ground it shoots straight ahead, but in the air it shoots diagonally down forward.
- When paired with Blackheart, if Mephisto finishes the opponent using the Crossover Combination attack, the word Armageddon (the name of one of his super moves) will appear twice (Armageddon Armageddon), since both characters use the same super move. A similar situation happens with a Captain America/U.S. Agent team, where that team's Crossover Combination would be called Star Star (Star and Stripes and Charging Star, regardless of which character is active).