Excavate for Secrets

This spell costs {2} less to cast if a player has
milled three or more cards this turn.
Consonance (When you cast this spell, if there is
another spell with the same mana value on the stack,
copy it. You may choose new targets for the copy.)
Reveal the top card of your library. Target player
mills X cards, where X is that card's mana value.
Then, put that card into your hand.