When Rotting Rats enters the battlefield, each player discards a card.
Unearth( : Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)
2/1/2009 When Rotting Rats’s enters-the-battlefield ability resolves, first the player whose turn it is chooses a card to discard, then each other player in turn order does the same, then all cards are discarded at the same time. No one sees what the other players are discarding before deciding which card to discard.