Rakdos the Defiler [Ravnica Allegiance Guild Kit] Human Mercenary Knight how would I know it

how would I know it worked

Set: Magic 2015 Tokens Type: Token Creature — Beast Rarity: Common

Set: Innistrad Type: Instant Rarity: Common Cost: {1}{W} Tap up to two target creatures

Set: Alliances Type: Creature — Human Advisor Rarity: Uncommon Cost: {2}{W} {3}

Set: Guildpact Type: Sorcery Rarity: Uncommon Cost: {2}{U} Replicate {2}{U} (When you cast this spell

Rakdos the Defiler [Ravnica Allegiance Guild Kit] Human Mercenary Knight how would I know itSet: Ravnica Allegiance Guild Kit Type: Legendary Creature Demon Rarity: Rare Cost: {2}{B}{B}{R}{R} Flying, trample Whenever Rakdos the Defiler attacks, sacrifice half the non Demon permanents you control, rounded up. Whenever Rakdos deals combat damage to a player, that player sacrifices half the non Demon permanents they control, rounded up.