Erratical

Entrance, Improvise
Whenever another creature enters the
battlefield, roll a d20.
1-5 | You gain 1 life. Erratical phases out.
6-19 | Erratical gains all that creature's
abilities until end of turn.
20 | Exile the top card of your library. You
may play it this turn without paying its
mana cost. Erratical phases out.
"I have no idea!"