Rock Hydra (Retro) [30th Anniversary Edition] Legendary Enchantment Creature lands you control have “{T}:

lands you control have “{T}: Add one mana of any color

except it has "Whenever this creature deals combat damage to a player

untap Time Vault

Sacrifice two other artifacts and/or creatures: Put an indestructible counter on Mondrak

you may cast that card and you may spend mana as though it were mana of any color to cast that spell

Rock Hydra (Retro) [30th Anniversary Edition] Legendary Enchantment Creature lands you control have “{T}:Set: 30th Anniversary Edition Type: Creature Hydra Rarity: Rare Cost: {X}{R}{R} Rock Hydra enters the battlefield with X +1 +1 counters on it. For each 1 damage that would be dealt to Rock Hydra, if it has a +1 +1 counter on it, remove a +1 +1 counter from it and prevent that 1 damage. {R}: Prevent the next 1 damage that would be dealt to Rock Hydra this turn. {R}{R}{R}: Put a +1 +1 counter on Rock Hydra. Activate only during your upkeep.