Sidisi, Regent of the Mire is a rare Legendary Creature — Zombie Snake Warlock card from Tarkir: Dragonstorm Promos (PTDM), collector number 92p. Current market price: $0.49 (foil $0.84), TCGplayer market prices via Scryfall.
{T}, Sacrifice a creature you control with mana value X other than Sidisi: Return target creature card with mana value X plus 1 from your graveyard to the battlefield. Activate only as a sorcery.