Petra Sphinx [Legends] Magic 2015 Your opponents can't gain life

Your opponents can't gain life

Set: Urza's Saga Type: Artifact Rarity: Uncommon Cost: {1} {1}

Set: Kaladesh Prerelease Promos Type: Legendary Planeswalker — Dovin Rarity: Mythic Cost: {2}{W}{U} +1: Until your next turn

but how do we get down

you gain 3 life and you may return up to one target creature card from your graveyard to your hand

Petra Sphinx [Legends] Magic 2015 Your opponents can't gain lifeSet: Legends Type: Creature Sphinx Rarity: Rare Cost: {2}{W}{W}{W} {T}: Target player chooses a card name, then reveals the top card of their library. If that card has the chosen name, that player puts it into their hand. If it doesn't, the player puts it into their graveyard. What walks on four legs in the morning, two legs in the afternoon, and three legs in the evening?