Braids, Arisen Nightmare [Dominaria United Prerelease Promos] SV118 and has "Whenever a player

and has "Whenever a player casts a spell or a creature attacks

Set: Sword & Shield: Battle Styles Type: Metal Rarity: Secret Rare Retreat cost: 0

Whenever you attack with Merry and another legendary creature

then return him to the battlefield transformed under his owner's control

Set: EX: Sandstorm Type: Colorless Rarity: Holo Rare Retreat cost: Colorless

Braids, Arisen Nightmare [Dominaria United Prerelease Promos] SV118 and has "Whenever a playerSet: Dominaria United Prerelease Promos Type: Legendary Creature Nightmare Rarity: Rare Cost: {1}{B}{B} At the beginning of your end step, you may sacrifice an artifact, creature, enchantment, land, or planeswalker. If you do, each opponent may sacrifice a permanent that shares a card type with it. For each opponent who doesn't, that player loses 2 life and you draw a card.