Changeling Sentinel

First strike Reinforce 1—1W (1W, Discard this card: Put a +1/+1 counter on target creature.)

Target player discards X cards at random.

Prowl 2B (You may cast this for its prowl cost if you dealt combat damage to a player this turn with a Goblin or Rogue.) When this creature enters, if its prowl cost was paid, search target opponent's library for three cards and exile them. Then that player shuffles.

Draw a card. Clash with an opponent. If you win, return Research the Deep to its owner's hand. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)

Draw X cards.

Flying U: Put this creature on top of its owner's library.

Whenever this creature attacks alone, it gets +1/+1 and gains trample until end of turn.

As this artifact enters, choose a creature type. Whenever you cast a spell of the chosen type, put a charge counter on this artifact. Creatures you control of the chosen type get +1/+1 for each charge counter on this artifact.