Six (Foil Etched) [Modern Horizons 3] Mutant Warrior you may pay {0} rather

you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less

Set: Junior Super Series Type: Creature — Goblin Shaman Rarity: Rare Cost: {2}{B} Other Goblin creatures you control get +1/+1

Brazen Borrower can block only creatures with flying

Set: HasCon 2017 Type: Token Creature — Dragon Rarity: Mythic Flying

you may destroy target artifact

Six (Foil Etched) [Modern Horizons 3] Mutant Warrior you may pay {0} ratherSet: Modern Horizons 3 Type: Legendary Creature Treefolk Rarity: Rare Cost: {2}{G} Reach Whenever Six attacks, mill three cards. You may put a land card from among them into your hand. As long as it's your turn, nonland permanent cards in your graveyard have retrace. (You may cast permanent cards from your graveyard by discarding a land card in addition to paying their other costs.)