Flying, trample Annihilator 1 (Whenever this creature attacks, defending player sacrifices a permanent.) If Mephistopheles would leave the battlefield, regenerate it, then transform it. 4/4
(Color: Black Red) Legendary Creature - Demon
Flying, trample, haste Dominate 2 (Whenever this creature attacks, gain control of two target permanents defending player controls for as long as you control this creature.) If Alpha Mephistopheles would leave the battlefield, regenerate it, then target opponent gains control of it.
You fell victim to one of the classic blunders - The most famous of which is "never get involved in an thread with GM_Champion" - but only slightly less well-known is this: "Never go in against AzureShade when card design is on the line!