Gold Myr

Felidar Guardian

When Felidar Guardian enters, you may exile another target permanent you control, then return that card to the battlefield under its owner's control.

Kruin Striker

Whenever another creature you control enters, Kruin Striker gets +1/+0 and gains trample until end of turn. (It can deal excess combat damage to the player or planeswalker it's attacking.)

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Plains

Palladium Myr

Restoration Angel

Flash
Flying
When Restoration Angel enters, you may exile target non-Angel creature you control, then return that card to the battlefield under your control.

Luminous Phantom

Flying
Whenever another creature you control leaves the battlefield, you gain 1 life.
If Luminous Phantom would be put into a graveyard from anywhere, exile it instead.

Lunarch Veteran

Whenever another creature you control enters, you gain 1 life.
Disturb {1}{W} (You may cast this card from your graveyard transformed for its disturb cost.)

Lunarch Veteran // Luminous Phantom

Icewind Stalwart

Protection Fighting Style — When Icewind Stalwart enters, exile up to one target non-Warrior creature you control, then return it to the battlefield under its owner's control.

Mountain

Wispweaver Angel

Flying
When Wispweaver Angel enters, you may exile another target creature you control, then return that card to the battlefield under its owner's control.