Vampire Vault

Mana Vault does not untap during your untap phase. At the end of your upkeep, if Mana Vault is tapped, it deals 1 damage to you. {4}: Untap Mana Vault at end of upkeep. Use this ability only during your upkeep. {T}Add three colorless mana to your mana pool. Play this ability as a mana source.