Riddler, Compulsive Puzzler

At the beginning of each player's upkeep, they mill
two cards for each Clue they control.

Whenever you commit a crime, each player
investigates. This ability triggers only once each
turn.

{t}, Sacrifice X Clues: Return target instant or
sorcery card with mana value X from your
graveyard to your hand. Activate only as a
sorcery.