Be'lakor, the Dark Master{3}{U}{B}{R}
Legendary Creature — Demon Noble
Prince of Chaos — When Be'lakor, the Dark Master enters the battlefield, you draw X cards and you lose X life, where X is the number of Demons you control.
Lord of Torment — Whenever another Demon enters the battlefield under your control, it deals damage equal to its power to any target.
Artist: Daarken