Old-Growth Dryads

When this creature enters, each opponent may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.

Rakdos Carnarium

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {B}{R}.

Plains

Glint Hawk

Flying
When this creature enters, sacrifice it unless you return an artifact you control to its owner's hand.

Eater of Days

Flying, trample
When this creature enters, you skip your next two turns.

Orzhov Basilica

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {W}{B}.

Lotus Field

Hexproof
This land enters tapped.
When this land enters, sacrifice two lands.
{T}: Add three mana of any one color.

Rupture Spire

This land enters tapped.
When this land enters, sacrifice it unless you pay {1}.
{T}: Add one mana of any color.

Drekavac

When this creature enters, sacrifice it unless you discard a noncreature card.

Serum Powder

{T}: Add {C}.
Any time you could mulligan and this card is in your hand, you may exile all the cards from your hand, then draw that many cards. (You can do this in addition to taking mulligans.)

Dust Elemental

Flash (You may cast this spell any time you could cast an instant.)
Flying; fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
When this creature enters, return three creatures you control to their owner's hand.

Strict Proctor

Flying
Whenever a permanent entering causes a triggered ability to trigger, counter that ability unless its controller pays {2}.

Hidden Horror

When this creature enters, sacrifice it unless you discard a creature card.

Boldwyr Heavyweights

Trample
When this creature enters, each opponent may search their library for a creature card and put it onto the battlefield. Then each player who searched their library this way shuffles.

Golgari Rot Farm

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {B}{G}.

Archway Commons

Ovinomancer

When Ovinomancer enters, sacrifice it unless you return three basic lands you control to their owner's hand.
{T}, Return Ovinomancer to its owner's hand: Destroy target creature. It can't be regenerated. That creature's controller creates a 0/1 green Sheep creature token.

Avatar of Discord

({B/R} can be paid with either {B} or {R}.)
Flying
When this creature enters, sacrifice it unless you discard two cards.