Veil, Spark Sleuth

At the beginning of your end step, look at the top
four cards of target opponent's library. You may
exile one of them face down with a Clue counter
on it, then that opponent shuffles. You may look
at the exiled card at any time.
{1}{r},{t}, Remove a Clue counter from a card
exiled with Veil: Reveal that card and Veil does
X damage to any target, where X is that card's
mana value.