Indoctrination Attendant

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Indoctrination Attendant enters, you may return another permanent you control to its owner's hand. If you do, create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block."

Saltskitter

Whenever another creature enters, exile Saltskitter. Return Saltskitter to the battlefield under its owner's control at the beginning of the next end step.

Changeling Hero

Changeling (This card is every creature type.)
Champion a creature (When this enters, sacrifice it unless you exile another creature you control. When this leaves the battlefield, that card returns to the battlefield.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Kor Cartographer

When Kor Cartographer enters, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

Search Party Captain

This spell costs {1} less to cast for each creature you attacked with this turn.
When Search Party Captain enters, draw a card.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Spirited Companion

When Spirited Companion enters, draw a card.

Kor Skyfisher

Flying
When Kor Skyfisher enters, return a permanent you control to its owner's hand.

Rambunctious Mutt

When Rambunctious Mutt enters, destroy target artifact or enchantment an opponent controls.

Guardians of Koilos

When Guardians of Koilos enters, you may return another target historic permanent you control to its owner's hand. (Artifacts, legendaries, and Sagas are historic.)

Draconian Gate-Bot

When Draconian Gate-Bot enters, choose one —
• Open an Attraction. (Put the top card of your Attraction deck onto the battlefield.)
• Destroy target Attraction. (It's put into its owner's junkyard.)

Soul Warden

Whenever another creature enters, you gain 1 life.

Stonehorn Dignitary

When Stonehorn Dignitary enters, target opponent skips their next combat phase.

Skyscanner

Flying
When Skyscanner enters, draw a card.

Inspiring Overseer

Flying
When this creature enters, you gain 1 life and draw a card.

Priest of Ancient Lore

When Priest of Ancient Lore enters, you gain 1 life and draw a card.

Whitemane Lion

Flash
When Whitemane Lion enters, return a creature you control to its owner's hand.