Zendikar Resurgent [Oath of the Gatewatch Prerelease Promos] Fifth Edition any time you could activate

any time you could activate a mana ability

MagicTheGathering

you may instead choose land or nonland and reveal cards from the top of your library until you reveal a card of the chosen kind

target player mills half their library

Set: Kaladesh Prerelease Promos Type: Legendary Artifact Rarity: Mythic Cost: {4} Whenever a permanent you control is put into a graveyard

Zendikar Resurgent [Oath of the Gatewatch Prerelease Promos] Fifth Edition any time you could activateSet: Oath of the Gatewatch Prerelease Promos Type: Enchantment Rarity: Rare Cost: {5}{G}{G} Whenever you tap a land for mana, add one mana of any type that land produced. (The types of mana are white, blue, black, red, green, and colorless.) Whenever you cast a creature spell, draw a card.