Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Negate

Agent of the Shadow Thieves

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, put a +1/+1 counter on this creature. It gains deathtouch and indestructible until end of turn."

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Scion of Halaster

Commander creatures you own have "The first time you would draw a card each turn, instead look at the top two cards of your library. Put one of them into your graveyard and the other back on top of your library. Then draw a card."

Blighted Agent

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Blighted Agent can't be blocked.

Buried Alive

Search your library for up to three creature cards, put them into your graveyard, then shuffle.

Stargaze

Look at twice X cards from the top of your library. Put X cards from among them into your hand and the rest into your graveyard. You lose X life.

Sword Coast Sailor

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, this creature can't be blocked this turn."

Titanoth Rex

Trample
Cycling {1}{G} ({1}{G}, Discard this card: Draw a card.)
When you cycle Titanoth Rex, put a trample counter on target creature you control.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Counterspell

Impervious Greatwurm

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Indestructible

Brawn

Trample
As long as Brawn is in your graveyard and you control a Forest, creatures you control have trample.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

The Mimeoplasm

As The Mimeoplasm enters, you may exile two creature cards from graveyards. If you do, it enters as a copy of one of those cards with a number of additional +1/+1 counters on it equal to the power of the other card.

Death's Shadow

Death's Shadow gets -X/-X, where X is your life total.

Ukkima, Stalking Shadow

Partner with Cazur, Ruthless Stalker (When this creature enters, target player may put Cazur into their hand from their library, then shuffle.)
Ukkima, Stalking Shadow can't be blocked.
When Ukkima leaves the battlefield, it deals X damage to target player and you gain X life, where X is its power.

Yargle and Multani

Curie, Emergent Intelligence

Whenever Curie, Emergent Intelligence deals combat damage to a player, draw cards equal to its base power.
{1}{U}, Exile another nontoken artifact creature you control: Curie becomes a copy of the exiled creature, except it has "Whenever this creature deals combat damage to a player, draw cards equal to its base power."