Mana Vault [Foreign Black Border] Rare Set: Legends Type: Creature —

Set: Legends Type: Creature — Beast Rarity: Rare Cost: {2}{R} {T}: Destroy target blue creature

This puzzle will be satisfying and enjoyable to construct for those who want to be challenged

Dragonlord Ojutai has hexproof as long as it's untapped

and yodeling

Mana Vault [Foreign Black Border] Rare Set: Legends Type: Creature —Set: Foreign Black Border Type: Artifact Rarity: Rare Cost: {1} Mana Vault doesn't untap during your untap step. At the beginning of your upkeep, you may pay {4}. If you do, untap Mana Vault. At the beginning of your draw step, if Mana Vault is tapped, it deals 1 damage to you. {T}: Add {C}{C}{C}.