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.

Mistbreath Elder

At the beginning of your upkeep, return another creature you control to its owner's hand. If you do, put a +1/+1 counter on this creature. Otherwise, you may return this creature to its owner's hand.

Coiling Stalker

Ninjutsu {1}{G} ({1}{G}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever this creature deals combat damage to a player, put a +1/+1 counter on target creature you control that doesn't have a +1/+1 counter on it.

Rambling Possum

Whenever this creature attacks while saddled, it gets +1/+2 until end of turn. Then you may return any number of creatures that saddled it this turn to their owner's hand.
Saddle 1 (Tap any number of other creatures you control with total power 1 or more: This Mount becomes saddled until end of turn. Saddle only as a sorcery.)

Forest

Roaring Primadox

At the beginning of your upkeep, return a creature you control to its owner's hand.

Cloudstone Curio

Whenever a nonartifact permanent you control enters, you may return another permanent you control that shares a permanent type with it to its owner's hand.

Decoction Module

Whenever a creature you control enters, you get {E} (an energy counter).
{4}, {T}: Return target creature you control to its owner's hand.

Spider-Ham, Peter Porker

When Spider-Ham enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Animal May-Ham — Other Spiders, Boars, Bats, Bears, Birds, Cats, Dogs, Frogs, Jackals, Lizards, Mice, Otters, Rabbits, Raccoons, Rats, Squirrels, Turtles, and Wolves you control get +1/+1.

Spider-Man, Brooklyn Visionary

Web-slinging {2}{G} (You may cast this spell for {2}{G} if you also return a tapped creature you control to its owner's hand.)
When Spider-Man enters, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Invasive Species

When this creature enters, return another permanent you control to its owner's hand.

Stampeding Serow

Trample
At the beginning of your upkeep, return a green creature you control to its owner's hand.

First Responder

Vigilance
At the beginning of your end step, you may return another creature you control to its owner's hand, then put a number of +1/+1 counters equal to that creature's power on this creature.

Stampeding Wildebeests

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
At the beginning of your upkeep, return a green creature you 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.

Wall Crawl

When this enchantment enters, create a 2/1 green Spider creature token with reach, then you gain 1 life for each Spider you control.
Spiders you control get +1/+1 and can't be blocked by creatures with defender.

Panharmonicon

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

Kappa Tech-Wrecker

Ninjutsu {1}{G}
This creature enters with a deathtouch counter on it.
Whenever this creature deals combat damage to a player, you may remove a deathtouch counter from it. When you do, exile target artifact or enchantment that player controls.

Spiders-Man, Heroic Horde

Web-slinging {4}{G}{G} (You may cast this spell for {4}{G}{G} if you also return a tapped creature you control to its owner's hand.)
When Spiders-Man enters, if they were cast using web-slinging, you gain 3 life and create two 2/1 green Spider creature tokens with reach.

Spring-Leaf Avenger

Ninjutsu {3}{G} ({3}{G}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever this creature deals combat damage to a player, return target permanent card from your graveyard to your hand.