Ajani's Comrade

Trample
At the beginning of combat on your turn, if you control an Ajani planeswalker, put a +1/+1 counter on Ajani's Comrade.

Acid Web Spider

Reach
When Acid Web Spider enters, you may destroy target Equipment.

Abundant Growth

Enchant land
When Abundant Growth enters, draw a card.
Enchanted land has "{T}: Add one mana of any color."

Ajani, Valiant Protector

+2: Put two +1/+1 counters on up to one target creature.
+1: Reveal cards from the top of your library until you reveal a creature card. Put that card into your hand and the rest on the bottom of your library in a random order.
−11: Put X +1/+1 counters on target creature, where X is your life total. That creature gains trample until end of turn.

Acidic Slime

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

Forest

Ainok Guide

When Ainok Guide enters, choose one —
• Put a +1/+1 counter on Ainok Guide.
• Search your library for a basic land card, reveal it, then shuffle and put that card on top.

Advocate of the Beast

At the beginning of your end step, put a +1/+1 counter on target Beast creature you control.

Aerial Predation

Destroy target creature with flying. You gain 2 life.

Aerie Bowmasters

Reach (This creature can block creatures with flying.)
Megamorph {5}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)