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.)

Chronomaton

{1}, {T}: Put a +1/+1 counter on this creature.

Hunter's Insight

Choose target creature you control. Whenever that creature deals combat damage to a player or planeswalker this turn, draw that many cards.

Arcbound Worker

Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Roaring Earth

Landfall — Whenever a land you control enters, put a +1/+1 counter on target creature or Vehicle you control.
Channel — {X}{G}{G}, Discard this card: Put X +1/+1 counters on target land you control. It becomes a 0/0 green Spirit creature with haste. It's still a land.

Herd Baloth

Whenever one or more +1/+1 counters are put on this creature, you may create a 4/4 green Beast creature token.

Phalanx Leader

Heroic — Whenever you cast a spell that targets this creature, put a +1/+1 counter on each creature you control.

Duty Beyond Death

As an additional cost to cast this spell, sacrifice a creature.
Creatures you control gain indestructible until end of turn. Put a +1/+1 counter on each creature you control. (Damage and effects that say "destroy" don't destroy those creatures.)

Wildwood Scourge

This creature enters with X +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on another non-Hydra creature you control, put a +1/+1 counter on this creature.

Pledge of Unity

Put a +1/+1 counter on each creature you control. You gain 1 life for each creature you control.

Faithful Watchdog

Vigilance
This creature enters with three +1/+1 counters on it.

Mindless Automaton

This creature enters with two +1/+1 counters on it.
{1}, Discard a card: Put a +1/+1 counter on this creature.
Remove two +1/+1 counters from this creature: Draw a card.

Inspiring Call

Draw a card for each creature you control with a +1/+1 counter on it. Those creatures gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

Kami of Whispered Hopes

If one or more +1/+1 counters would be put on a permanent you control, that many plus one +1/+1 counters are put on that permanent instead.
{T}: Add X mana of any one color, where X is this creature's power.

Rosie Cotton of South Lane

When Rosie Cotton enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Whenever you create a token, put a +1/+1 counter on target creature you control other than Rosie Cotton.

Colossal Majesty

At the beginning of your upkeep, if you control a creature with power 4 or greater, draw a card.

Tuskguard Captain

Outlast {G} ({G}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has trample.

Triskelion

This creature enters with three +1/+1 counters on it.
Remove a +1/+1 counter from this creature: It deals 1 damage to any target.

Ainok Bond-Kin

Outlast {1}{W} ({1}{W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has first strike.

Star Pupil

This creature enters with a +1/+1 counter on it.
When this creature dies, put its counters on target creature you control.

Generous Gift

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

Botanical Brawler

Trample
This creature enters with two +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on another permanent you control, if it's the first time +1/+1 counters have been put on that permanent this turn, put a +1/+1 counter on this creature.

Hamza, Guardian of Arashin

This spell costs {1} less to cast for each creature you control with a +1/+1 counter on it.
Creature spells you cast cost {1} less to cast for each creature you control with a +1/+1 counter on it.

Anafenza, Kin-Tree Spirit

Whenever another nontoken creature you control enters, bolster 1. (Choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.)

Slurrk, All-Ingesting

Slurrk enters with five +1/+1 counters on it.
Whenever Slurrk or another creature you control dies, if it had a +1/+1 counter on it, put a +1/+1 counter on each creature you control that has a +1/+1 counter on it.
Partner (You can have two commanders if both have partner.)

Renata, Called to the Hunt

Renata's power is equal to your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)
Each other creature you control enters with an additional +1/+1 counter on it.

Avatar of the Resolute

Reach, trample
This creature enters with a +1/+1 counter on it for each other creature you control with a +1/+1 counter on it.

Jiang Yanggu, Wildcrafter

Each creature you control with a +1/+1 counter on it has "{T}: Add one mana of any color."
−1: Put a +1/+1 counter on target creature.

Plains

Return to Nature

Choose one —
• Destroy target artifact.
• Destroy target enchantment.
• Exile target card from a graveyard.

Unbounded Potential

Choose one —
• Put a +1/+1 counter on each of up to two target creatures.
• Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Entwine {3}{W} (Choose both if you pay the entwine cost.)

Rishkar, Peema Renegade

When Rishkar enters, put a +1/+1 counter on each of up to two target creatures.
Each creature you control with a counter on it has "{T}: Add {G}."

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Forest

Towashi Guide-Bot

When this creature enters, put a +1/+1 counter on target creature you control.
{4}, {T}: Draw a card. This ability costs {1} less to activate for each modified creature you control. (Equipment, Auras you control, and counters are modifications.)

Master Chef

Commander creatures you own have "This creature enters with an additional +1/+1 counter on it" and "Other creatures you control enter with an additional +1/+1 counter on them."

Command Tower

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

Gift of the Viper

Put a +1/+1 counter, a reach counter, and a deathtouch counter on target creature. Untap it.

Llanowar Reborn

This land enters tapped.
{T}: Add {G}.
Graft 1 (This land enters with a +1/+1 counter on it. Whenever a creature enters, you may move a +1/+1 counter from this land onto it.)

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Kutzil, Malamet Exemplar

Your opponents can't cast spells during your turn.
Whenever one or more creatures you control each with power greater than its base power deals combat damage to a player, draw a card.

Sporeback Troll

Graft 2 (This creature enters with two +1/+1 counters on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{1}{G}: Regenerate target creature with a +1/+1 counter on it.

Beast Within

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

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Kirtar's Wrath

Destroy all creatures. They can't be regenerated.
Threshold — If seven or more cards are in your graveyard, instead destroy all creatures, then create two 1/1 white Spirit creature tokens with flying. Creatures destroyed this way can't be regenerated.

Arcane Signet

Armorcraft Judge

When this creature enters, draw a card for each creature you control with a +1/+1 counter on it.

Spike Feeder

This creature enters with two +1/+1 counters on it.
{2}, Remove a +1/+1 counter from this creature: Put a +1/+1 counter on target creature.
Remove a +1/+1 counter from this creature: You gain 2 life.

Spike Drone

This creature enters with a +1/+1 counter on it.
{2}, Remove a +1/+1 counter from this creature: Put a +1/+1 counter on target creature.

Cankerbloom

{1}, Sacrifice this creature: Choose one —
• Destroy target artifact.
• Destroy target enchantment.
• Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Abzan Falconer

Outlast {W} ({W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has flying.

Garruk's Uprising

When this enchantment enters, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever a creature you control with power 4 or greater enters, draw a card.

Loyal Guardian

Trample
Lieutenant — At the beginning of combat on your turn, if you control your commander, put a +1/+1 counter on each creature you control.

Evolution Sage

Landfall — Whenever a land you control enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Wren's Run Hydra

Reach
This creature enters with X +1/+1 counters on it.
Reinforce X—{X}{G}{G} ({X}{G}{G}, Discard this card: Put X +1/+1 counters on target creature.)

Unravel the Aether

Choose target artifact or enchantment. Its owner shuffles it into their library.

Evolution Witness

{1}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Whenever one or more +1/+1 counters are put on this creature, return target permanent card from your graveyard to your hand.

Fertilid

This creature enters with two +1/+1 counters on it.
{1}{G}, Remove a +1/+1 counter from this creature: Target player searches their library for a basic land card, puts it onto the battlefield tapped, then shuffles.

Stroke of Midnight

Destroy target nonland permanent. Its controller creates a 1/1 white Human creature token.

Experiment One

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Remove two +1/+1 counters from this creature: Regenerate it. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Skarrgan Pit-Skulk

Bloodthirst 1 (If an opponent was dealt damage this turn, this creature enters with a +1/+1 counter on it.)
Creatures with power less than this creature's power can't block it.

Duskshell Crawler

When this creature enters, put a +1/+1 counter on target creature.
Each creature you control with a +1/+1 counter on it has trample. (It can deal excess combat damage to the player or planeswalker it's attacking.)

Ivy Lane Denizen

Whenever another green creature you control enters, put a +1/+1 counter on target creature.

Wild Growth

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G}.

Good-Fortune Unicorn

Whenever another creature you control enters, put a +1/+1 counter on that creature.