The Fifth Alias is a rare Legendary Creature — Shapeshifter card from Unknown Event (UNK), collector number RZ03g.
Before the game begins, if The Fifth Alias is your commander or in your deck, secretly make a list of five nonland cards in your deck. (Don't forget to do this!) As you draw a card on your list, you may reveal it, show it was on the list, and exclaim its name. If you do, cast it without paying its mana cost.