Spawn of Mayhem (Promo Pack) [Ravnica Allegiance Promos] Phenomenon It has "Sacrifice this creature:

It has "Sacrifice this creature: Add {C}

that opponent's monster loses 1000 ATK during that damage calculation only

While this card points to a Synchro Monster(s)

but also what could be

Set: Tactical Evolution Card type: Gemini Monster Rarity: Secret Rare Attack: 2100 Defense: 800 This card is treated as a Normal Monster while face-up on the field or in the Graveyard

Spawn of Mayhem (Promo Pack) [Ravnica Allegiance Promos] Phenomenon It has "Sacrifice this creature:Set: Ravnica Allegiance Promos Type: Creature Demon Rarity: Mythic Cost: {2}{B}{B} Spectacle {1}{B}{B} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.) Flying, trample At the beginning of your upkeep, Spawn of Mayhem deals 1 damage to each player. Then if you have 10 or less life, put a +1 +1 counter on Spawn of Mayhem.