Acererak the Archlich

When Acererak the Archlich enters, if you haven't completed Tomb of Annihilation, return Acererak the Archlich to its owner's hand and venture into the dungeon.
Whenever Acererak the Archlich attacks, for each opponent, you create a 2/2 black Zombie creature token unless that player sacrifices a creature of their choice.

Elvish Visionary

When Elvish Visionary enters, draw a card.

Llanowar Visionary

When Llanowar Visionary enters, draw a card.
{T}: Add {G}.

Baleful Strix

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

Stonecloaker

Flash
Flying
When Stonecloaker enters, return a creature you control to its owner's hand.
When Stonecloaker enters, exile target card from a graveyard.

Skyscanner

Flying
When Skyscanner enters, draw a card.

Nantuko Shaman

When Nantuko Shaman enters, if you control no tapped lands, draw a card.
Suspend 1—{2}{G}{G} (Rather than cast this card from your hand, you may pay {2}{G}{G} and exile it with a time counter on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Merchant of Secrets

When Merchant of Secrets enters, draw a card.

Inspiring Overseer

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

Parasitic Strix

Flying
When Parasitic Strix enters, if you control a black permanent, target player loses 2 life and you gain 2 life.

Cavern Harpy

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

Priest of Ancient Lore

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

Generous Stray

Ice-Fang Coatl

Flash
Flying
When Ice-Fang Coatl enters, draw a card.
Ice-Fang Coatl has deathtouch as long as you control at least three other snow permanents.

Multani's Acolyte

Echo {G}{G} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Multani's Acolyte enters, draw a card.

Aluren

Any player may cast creature spells with mana value 3 or less without paying their mana costs and as though they had flash.