Crystal Shard

{3}, {T} or {U}, {T}: Return target creature to its owner's hand unless its controller pays {1}.

The Master, Formed Anew

Body Thief — When you cast this spell, you may exile a creature you control and put a takeover counter on it.
You may have The Master, Formed Anew enter the battlefield as a copy of a creature card in exile with a takeover counter on it.

Peregrine Drake

Flying
When Peregrine Drake enters the battlefield, untap up to five lands.

Portal of Sanctuary

{1}, {T}: Return target creature you control and each Aura attached to it to their owners' hands. Activate only during your turn.

Solemn Simulacrum

When Solemn Simulacrum enters the battlefield, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Gyruda, Doom of Depths

Companion — Your starting deck contains only cards with even mana values. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
When Gyruda enters the battlefield, each player mills four cards. Put a creature card with an even mana value from among the milled cards onto the battlefield under your control.

Study Hall

{T}: Add {C}.
{1}, {T}: Add one mana of any color. When you spend this mana to cast your commander, scry X, where X is the number of times it's been cast from the command zone this game.

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters the battlefield, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Dimir Aqueduct

Dimir Aqueduct enters the battlefield tapped.
When Dimir Aqueduct enters the battlefield, return a land you control to its owner's hand.
{T}: Add {U}{B}.

Whelming Wave

Return all creatures to their owners' hands except for Krakens, Leviathans, Octopuses, and Serpents.

Curfew

Each player returns a creature they control to its owner's hand.

Swamp

Cavern Harpy

Flying
When Cavern Harpy enters the battlefield, return a blue or black creature you control to its owner's hand.
Pay 1 life: Return Cavern Harpy to its owner's hand.

Island

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Panharmonicon

If an artifact or creature entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Shrieking Drake

Flying
When Shrieking Drake enters the battlefield, return a creature you control to its owner's hand.

Snap

Return target creature to its owner's hand. Untap up to two lands.

Baleful Strix

Flying, deathtouch
When Baleful Strix enters the battlefield, draw a card.

Evacuation

Return all creatures to their owners' hands.

Dream Stalker

When Dream Stalker enters the battlefield, return a permanent you control to its owner's hand.

Opal Palace

{T}: Add {C}.
{1}, {T}: Add one mana of any color in your commander's color identity. If you spend this mana to cast your commander, it enters the battlefield with a number of additional +1/+1 counters on it equal to the number of times it's been cast from the command zone this game.

Echo Storm

When you cast this spell, copy it for each time you've cast your commander from the command zone this game. You may choose new targets for the copies.
Create a token that's a copy of target artifact.

Vantress Visions

Copy target activated or triggered ability you control. You may choose new targets for the copy.

Virtue of Knowledge

If a permanent entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Virtue of Knowledge // Vantress Visions

Umbilicus

At the beginning of each player's upkeep, that player may pay 2 life. If they don't, they return a permanent they control to its owner's hand.

Blood Clock

At the beginning of each player's upkeep, that player returns a permanent they control to its owner's hand unless they pay 2 life.

Candlekeep Sage

Commander creatures you own have "When this creature enters or leaves the battlefield, draw a card."

Skull Storm

When you cast this spell, copy it for each time you've cast your commander from the command zone this game.
Each opponent sacrifices a creature. Each opponent who can't loses half their life, rounded up.

Dimir Signet

Massacre Girl

Menace
When Massacre Girl enters the battlefield, each other creature gets -1/-1 until end of turn. Whenever a creature dies this turn, each creature other than Massacre Girl gets -1/-1 until end of turn.