Ob Nixilis of the Black Oath is a rare Legendary Planeswalker — Nixilis card from Commander Masters (CMM), collector number 176. Current market price: $1.14 (foil $1.58), TCGplayer market prices via Scryfall.
+2: Each opponent loses 1 life. You gain life equal to the life lost this way. −2: Create a 5/5 black Demon creature token with flying. You lose 2 life. −8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power." Ob Nixilis of the Black Oath can be your commander.