Creature - Crab Beast 3/3, 4U (5) Morph {4}{U} (You may play this face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When Chromeshell Crab is turned face up, you may exchange control of target creature you control and target creature an opponent controls.1
Illus. Ron Spencer
The trigger occurs when you use the Morph ability to turn the card face up, or when an effect turns it face up. It will not trigger on being revealed or on leaving play. [Legions FAQ 2003/01/23]
You choose the two target creatures when you place the ability on the stack. You do not have to choose this card. You choose whether or not to do the exchange on resolution. [Legions FAQ 2003/01/23]
The exchange fails if either target is not still in play at that time. [D'Angelo 2003/02/01]
The exchange fails if either you no longer control your creature or the other creature is now controlled by you. [DeLaney 2003/03/19]
The creatures cannot attack until you start a turn with them under your control. So you cannot swap and then attack. [D'Angelo 2003/09/08]
Legions
(Rare)