Geist Trappers

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, both creatures have reach.

Island

Druid's Familiar

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, each of those creatures gets +2/+2.

Elgaud Shieldmate

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, both creatures have hexproof. (They can't be the targets of spells or abilities your opponents control.)

Joint Assault

Target creature gets +2/+2 until end of turn. If it's paired with a creature, that creature also gets +2/+2 until end of turn.

Wingcrafter

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, both creatures have flying.

Flowering Lumberknot

This creature can't attack or block unless it's paired with a creature with soulbond.

Wolfir Silverheart

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, each of those creatures gets +4/+4.

Llanowar Elves

Lair Delve

Reveal the top two cards of your library. Put all creature and land cards revealed this way into your hand and the rest on the bottom of your library in any order.

Acidic Slime

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
When this creature enters, destroy target artifact, enchantment, or land.

Latch Seeker

Vorstclaw

Pathbreaker Wurm

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, both creatures have trample.

Overrun

Creatures you control get +3/+3 and gain trample until end of turn. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)

Nephalia Smuggler

{3}{U}, {T}: Exile another target creature you control, then return that card to the battlefield under your control.

Nightshade Peddler

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, both creatures have deathtouch.

Trusted Forcemage

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, each of those creatures gets +1/+1.

Runeclaw Bear

Wolfir Avenger

Flash (You may cast this spell any time you could cast an instant.)
{1}{G}: Regenerate this creature.

Ice Cage

Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.
When enchanted creature becomes the target of a spell or ability, destroy this Aura.

Forest

Tandem Lookout

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Tandem Lookout is paired with another creature, each of those creatures has "Whenever this creature deals damage to an opponent, draw a card."