Merfolk Windrobber

Flying
Whenever Merfolk Windrobber deals combat damage to a player, that player mills a card. (They put the top card of their library into their graveyard.)
Sacrifice Merfolk Windrobber: Draw a card. Activate only if an opponent has eight or more cards in their graveyard.

Thought Scour

Target player mills two cards.
Draw a card.

Screeching Silcaw

Flying
Metalcraft — Whenever Screeching Silcaw deals combat damage to a player, if you control three or more artifacts, that player mills four cards.

Seat of the Synod

Island

Chronic Flooding

Enchant land
Whenever enchanted land becomes tapped, its controller mills three cards.

Stream of Thought

Target player mills four cards. You shuffle up to four cards from your graveyard into your library.
Replicate {2}{U}{U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.