Arcane Adaptation

As Arcane Adaptation enters, choose a creature type.
Creatures you control are the chosen type in addition to their other types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.

Avenger of Zendikar

When Avenger of Zendikar enters, create a 0/1 green Plant creature token for each land you control.
Landfall — Whenever a land you control enters, you may put a +1/+1 counter on each Plant creature you control.

Spectral Arcanist

Flying
When Spectral Arcanist enters, you may cast an instant or sorcery spell with mana value less than or equal to the number of Spirits you control from a graveyard without paying its mana cost. If that spell would be put into a graveyard, exile it instead.

Mana Echoes

Whenever a creature enters, you may add an amount of {C} equal to the number of creatures you control that share a creature type with it.

Bishop of Wings

Whenever an Angel you control enters, you gain 4 life.
Whenever an Angel you control dies, create a 1/1 white Spirit creature token with flying.

Coordinated Barrage

Choose a creature type. Coordinated Barrage deals damage to target attacking or blocking creature equal to the number of permanents you control of the chosen type.

Peer Pressure

Choose a creature type. If you control more creatures of that type than each other player, you gain control of all creatures of that type. (This effect lasts indefinitely.)

Aura Shards

Whenever a creature you control enters, you may destroy target artifact or enchantment.

Silumgar, the Drifting Death

Flying, hexproof
Whenever a Dragon you control attacks, creatures defending player controls get -1/-1 until end of turn.

Runebound Wolf

{3}{R}, {T}: Runebound Wolf deals damage equal to the number of Wolves and Werewolves you control to target opponent.

Admiral Beckett Brass

Other Pirates you control get +1/+1.
At the beginning of your end step, gain control of target nonland permanent controlled by a player who was dealt combat damage by three or more Pirates this turn.

Unified Strike

Exile target attacking creature if its power is less than or equal to the number of Soldiers on the battlefield.

Gilt-Leaf Archdruid

Whenever you cast a Druid spell, you may draw a card.
Tap seven untapped Druids you control: Gain control of all lands target player controls.

Munitions Expert

Flash
When Munitions Expert enters, you may have it deal damage to target creature or planeswalker equal to the number of Goblins you control.

Pack Rat

Pack Rat's power and toughness are each equal to the number of Rats you control.
{2}{B}, Discard a card: Create a token that's a copy of Pack Rat.

Kessig Malcontents

When Kessig Malcontents enters, it deals damage to target player or planeswalker equal to the number of Humans you control.

Volley Veteran

When Volley Veteran enters, it deals damage to target creature an opponent controls equal to the number of Goblins you control.

Breeches, Brazen Plunderer

Menace
Whenever one or more Pirates you control deal damage to your opponents, exile the top card of each of those opponents' libraries. You may play those cards this turn, and you may spend mana as though it were mana of any color to cast those spells.
Partner (You can have two commanders if both have partner.)

Captivating Vampire

Other Vampire creatures you control get +1/+1.
Tap five untapped Vampires you control: Gain control of target creature. It becomes a Vampire in addition to its other types.

Hobgoblin Bandit Lord

Other Goblins you control get +1/+1.
{R}, {T}: Hobgoblin Bandit Lord deals damage equal to the number of Goblins that entered the battlefield under your control this turn to any target.

Goblin War Strike

Goblin War Strike deals damage to target player or planeswalker equal to the number of Goblins you control.

Thundercloud Shaman

When Thundercloud Shaman enters, it deals damage equal to the number of Giants you control to each non-Giant creature.

Katilda's Rising Dawn

Enchant creature
Enchanted creature has flying, lifelink, and protection from Vampires, and it gets +X/+X, where X is the number of permanents you control that are Spirits and/or enchantments.
If Katilda's Rising Dawn would be put into a graveyard from anywhere, exile it instead.

Katilda, Dawnhart Martyr

Flying, lifelink, protection from Vampires
Katilda, Dawnhart Martyr's power and toughness are each equal to the number of permanents you control that are Spirits and/or enchantments.
Disturb {3}{W}{W} (You may cast this card from your graveyard transformed for its disturb cost.)

Katilda, Dawnhart Martyr // Katilda's Rising Dawn

Malakir Bloodwitch

Flying, protection from white
When Malakir Bloodwitch enters, each opponent loses life equal to the number of Vampires you control. You gain life equal to the life lost this way.

Rin and Seri, Inseparable

Whenever you cast a Dog spell, create a 1/1 green Cat creature token.
Whenever you cast a Cat spell, create a 1/1 white Dog creature token.
{R}{G}{W}, {T}: Rin and Seri, Inseparable deals damage to any target equal to the number of Dogs you control. You gain life equal to the number of Cats you control.

Shaman of the Pack

When Shaman of the Pack enters, target opponent loses life equal to the number of Elves you control.

Tuktuk Scrapper

Whenever Tuktuk Scrapper or another Ally you control enters, you may destroy target artifact. If that artifact is put into a graveyard this way, Tuktuk Scrapper deals damage to that artifact's controller equal to the number of Allies you control.

Ondu Cleric

Whenever Ondu Cleric or another Ally you control enters, you may gain life equal to the number of Allies you control.

Aegar, the Freezing Flame

Whenever a creature or planeswalker an opponent controls is dealt excess damage, if a Giant, Wizard, or spell you controlled dealt damage to it this turn, draw a card.

Aether Charge

Whenever a Beast you control enters, you may have it deal 4 damage to target opponent or planeswalker.

Coercive Recruiter

Whenever Coercive Recruiter or another Pirate you control enters, gain control of target creature until end of turn. Untap that creature. Until end of turn, it gains haste and becomes a Pirate in addition to its other types.

Reaper King

({2/W} can be paid with any two mana or with {W}. This card's mana value is 10.)
Other Scarecrow creatures you control get +1/+1.
Whenever another Scarecrow you control enters, destroy target permanent.

Agadeem Occultist

{T}: Put target creature card from an opponent's graveyard onto the battlefield under your control if its mana value is less than or equal to the number of Allies you control.

Atla Palani, Nest Tender

{2}, {T}: Create a 0/1 green Egg creature token with defender.
Whenever an Egg you control dies, reveal cards from the top of your library until you reveal a creature card. Put that card onto the battlefield and the rest on the bottom of your library in a random order.

Thrull Champion

Thrull creatures get +1/+1.
{T}: Gain control of target Thrull for as long as you control Thrull Champion.