Petra Sphinx [Legends] Mirrodin Besieged In the reflection

In the reflection

−2: Reveal the top four cards of your library

Set: Unhinged Type: Legendary Creature — Human Designer Rare Cost: {3}{U}{U} You may play cards as though they were other cards of your choice with the same mana cost

Set: Beta Edition Type: Artifact Rarity: Rare Cost: {2} Time Vault enters the battlefield tapped

Petra Sphinx [Legends] Mirrodin Besieged In the reflectionSet: Legends Type: Creature Sphinx 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?