Walking Ballista

This creature enters with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on this creature.
Remove a +1/+1 counter from this creature: It deals 1 damage to any target.

Tamiyo's Safekeeping

Target permanent you control gains hexproof and indestructible until end of turn. You gain 2 life. (A permanent with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Stonecoil Serpent

Reach, trample, protection from multicolored
This creature enters with X +1/+1 counters on it.

Flooded Grove

{T}: Add {C}.
{G/U}, {T}: Add {G}{G}, {G}{U}, or {U}{U}.

Mutant's Prey

Target creature you control with a +1/+1 counter on it fights target creature an opponent controls. (Each deals damage equal to its power to the other.)

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Crimson Kobolds

Mountain

Endless One

This creature enters with X +1/+1 counters on it.

Hangarback Walker

This creature enters with X +1/+1 counters on it.
When this creature dies, create a 1/1 colorless Thopter artifact creature token with flying for each +1/+1 counter on this creature.
{1}, {T}: Put a +1/+1 counter on this creature.

Memnite

Apocalypse Hydra

This creature enters with X +1/+1 counters on it. If X is 5 or more, it enters with an additional X +1/+1 counters on it.
{1}{R}, Remove a +1/+1 counter from this creature: It deals 1 damage to any target.

Kobolds of Kher Keep

Forest

Stomping Ground

({T}: Add {R} or {G}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Crookshank Kobolds

Animar, Soul of Elements

Protection from white and from black
Whenever you cast a creature spell, put a +1/+1 counter on Animar.
Creature spells you cast cost {1} less to cast for each +1/+1 counter on Animar.

Shield Sphere

Defender
Whenever this creature blocks, put a -0/-1 counter on it.

Turn Aside

Counter target spell that targets a permanent you control.

Season of Growth

Whenever a creature you control enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Whenever you cast a spell that targets a creature you control, draw a card.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Wildborn Preserver

Flash (You may cast this spell any time you could cast an instant.)
Reach (This creature can block creatures with flying.)
Whenever another non-Human creature you control enters, you may pay {X}. When you do, put X +1/+1 counters on this creature.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Lifeblood Hydra

Trample
This creature enters with X +1/+1 counters on it.
When this creature dies, you gain life and draw cards equal to its power.

Ochre Jelly

Trample
This creature enters with X +1/+1 counters on it.
Split — When this creature dies, if it had two or more +1/+1 counters on it, create a token that's a copy of it at the beginning of the next end step. The token enters with half that many +1/+1 counters on it, rounded down.

Rograkh, Son of Rohgahh

First strike, menace, trample
Partner (You can have two commanders if both have partner.)

Shifting Wall

Defender (This creature can't attack.)
This creature enters with X +1/+1 counters on it.

Island

Ugin's Conjurant

This creature enters with X +1/+1 counters on it.
If damage would be dealt to this creature while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from this creature.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Cryptic Trilobite

This creature enters with X +1/+1 counters on it.
Remove a +1/+1 counter from this creature: Add {C}{C}. Spend this mana only to activate abilities.
{1}, {T}: Put a +1/+1 counter on this creature.

Phyrexian Walker

Force of Negation

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.
Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Ornithopter

Steam Vents

({T}: Add {U} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Phyrexian Marauder

This creature enters with X +1/+1 counters on it.
This creature can't block.
This creature can't attack unless you pay {1} for each +1/+1 counter on it.

Neverwinter Hydra

As this creature enters, roll X d6. It enters with a number of +1/+1 counters on it equal to the total of those results.
Trample
Ward {4} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)

Hooded Hydra

This creature enters with X +1/+1 counters on it.
When this creature dies, create a 1/1 green Snake creature token for each +1/+1 counter on it.
Morph {3}{G}{G}
As this creature is turned face up, put five +1/+1 counters on it.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Claim the Firstborn

Gain control of target creature with mana value 3 or less until end of turn. Untap that creature. It gains haste until end of turn.