Rin and Seri, Inseparable (Buy-A-Box) [Core Set 2021] MON000-CF but it is necessary

but it is necessary

that player exiles the top card of their library

then an opponent gains control of them

Set: Core Set 2019 Prerelease Promos Type: Legendary Creature — Dragon Rarity: Rare Cost: {4}{R}{R} Flying

each other non-Aura enchantment you control is a creature in addition to its other types and has base power and base toughness each equal to its converted mana cost

Rin and Seri, Inseparable (Buy-A-Box) [Core Set 2021] MON000-CF but it is necessarySet: Core Set 2021 Type: Legendary Creature Dog Cat Rarity: Mythic Cost: {1}{R}{G}{W} Whenever you cast a Dog spell, create a 1 1 green Cat creature token. Whenever you cast a Cat spell, create a 1 1 white Dog creature token. {R}{G}{W}, {T}: Rin and Seri, Inseparable deals damage to any target equal to the number of Dogs you control. You gain life equal to the number of Cats you control.