Champion of Stray Souls is a mythic Creature — Skeleton Warrior card from Commander Anthology (CMA), collector number 51. Current market price: $0.36, TCGplayer market prices via Scryfall.
{3}{B}{B}, {T}, Sacrifice X other creatures: Return X target creature cards from your graveyard to the battlefield. {5}{B}{B}: Put this card from your graveyard on top of your library.