Mox Diamond [From the Vault: Relics] Token Creature −3: You may cast target

−3: You may cast target instant or sorcery card from your graveyard this turn

Set: Modern Masters Type: Instant — Arcane Rarity: Uncommon Cost: {1}{B}{B} If you control a Swamp

Voice of Nightmares

change Halfdane's base power and toughness to the power and toughness of target creature other than Halfdane until the end of your next upkeep

Sometimes it's not

Mox Diamond [From the Vault: Relics] Token Creature −3: You may cast targetSet: From the Vault: Relics Type: Artifact Rarity: Mythic Cost: {0} If Mox Diamond would enter the battlefield, you may discard a land card instead. If you do, put Mox Diamond onto the battlefield. If you don't, put it into its owner's graveyard. {T}: Add one mana of any color.