You can't cast Rakdos unless an opponent lost life this turn.
Flying, trample
Creature spells you cast cost less to cast for each 1 life your opponents have lost this turn.
Deal damage to opponents to unlock massive cost reductions, then dump expensive creatures (often huge or free) onto the battlefield for explosive turns. Early game you ping opponents with pingers, Shocklands, and aggression, then chain out big bodies and game-enders once life loss accumulates. You win by overwhelming the board with cheated-out fatties and combo payoffs.
Can deploy multiple expensive creatures in a single turn for huge tempo swings
Self-fueling: even fetchlands, painlands, and your own pingers enable the discount
Eldrazi and big-mana creatures become absurdly cheap or free
Built-in evasion (flying, trample) makes Rakdos a real clock himself
Commander tax-like restriction: can't even cast Rakdos until an opponent loses life
Discount only applies to creatures—no help for instants, sorceries, or artifacts/enchantments
Heavily dependent on Rakdos staying on the battlefield; gets answered easily
Vulnerable to lifegain and fog effects that blunt your damage engine
Stumbles if your opening hand lacks early life-loss enablers
Every fatty you slam deals damage on entry, fueling more discounts and ending games.
Add reliable repeatable pingers (Spear Spewer, Cunning Sparkmage, Goblin Sharpshooter) and incidental life-loss sources so the engine never stalls. Lean into high-value bombs—It That Betrays, Artisan of Kozilek, Ulamog—plus reanimation to abuse the discount, and include fast mana (Sol Ring, Mana Vault, Jeweled Lotus) to deploy Rakdos and follow-ups early. Tighten the mana base with fetch/painlands that ping yourself or opponents and add protection like Lightning Greaves to keep Rakdos sticking.
Legendary Creature — Demon
less to cast for each 1 life your opponents have lost this turn.