msem-instigator

Ravenous Hydra enters with X +1/+1 counters on it.
Whenever Ravenous Hydra deals combat damage, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another kind of a counter already there.)

When Renatured Vines enters, draw a card and create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Renatured Vines power and toughness are each equal to the number of cards in your hand.

Trample
Rift Prowler enters with X +1/+1 counters on it, where X is your fealty to Forests. (Each Forest you control counts towards your fealty to Forests.)

Trample
Savage Mammoth gets +1/+1 for each land you control.
Ride {4}{G} ({4}{G}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Scion of the Wild's power and toughness are each equal to the number of creatures you control.

Pressure {2}{G}{G} (You may cast this spell for its pressure cost if there are seven or more cards in your graveyard.)
Trample, hexproof
Shambling Dreadreef's power and toughness are each equal to the total number of land cards you own on the battlefield and in your graveyard.

Shambling Hive power and toughness are each equal to the number of Insects you control.
Shambling Hive has vigilance as long as you control four or more Insects, and has trample as long as you control eight or more Insects.

Vigilance
Shuye, Forever Watching's power and toughness are each equal to the number of noncreature permanents you don't control.

Soulraving Hunt's power and toughness are each equal to the number of lands you control.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Swarm of Sporemites gets +1/+1 for each creature card and Revelation card in your graveyard.

Tarmovore's power and toughness are each equal to twice the number of card types among cards in all graveyards.

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
Tenacious Brawler enters with X +1/+1 counters on it.

Terra Novea's power and toughness are each equal to the number of permanents you control.
{T}: Add {G} for each land you control.

Flash
Thorn-Touch Abomination enters with X +1/+1 counters on it.

Trample, haste
Thriving Hydra enters with four +1/+1 counters on it.
When Thriving Hydra enters, for each other creature you control, put X +1/+1 counters on that creature, where X is four minus its power.
Whenever Thriving Hydra attacks, double the number of +1/+1 counters on each creature you control.

Unending Slime enters with X +1/+1 counters on it.
{2}{G}{G}{G}: Return Unending Slime from your graveyard to your hand.

Vigorbreath Scourge enters with X +1/+1 counters on it.
Whenever Vigorbreath Scourge attacks, it gets +X/+X until end of turn, where X is your devotion to green. Then if its power is 6 or greater, draw a card. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Vitalhydra enters with twice X +1/+1 counters on it.
Each other creature you control enters with a number of additional +1/+1 counters on it equal to the number of +1/+1 counters on Vitalhydra.

Warden of the Fronds' power and toughness are each equal to the number of Forests you control.
Warden of the Fronds has indestructible as long as you control five or more lands.

As Wayward Wanderers enters, you may have it become X/X with ward {X} and “Other creatures you control have base power and toughness X/X.”
{1}{G}: Return Wayward Wanderers to its owner's hand.

You may cast What Remains of Samuel Quinn from your graveyard and from the battlefield. It costs {G}{G} more to cast this way.
What Remains of Samuel Quinn enters with your choice of X counters from among +1/+1, vigilance, reach, and trample.

Trample
World Tender's power and toughness are each equal to twice the number of differently named lands you control.

You may have Better Half enter as a copy of any creature on the battlefield, except it's a Reflection in addition to its other creature types and it has distorted. (It can be blocked by tapped creatures but not untapped creatures.)

Flying, ward {2}
Intisuyu's Masterpiece gets +X/+X, where X is the number of artifacts and/or enchantments you control.

Flying
Tawny Prophet enters with three +1/+1 counters on it.
{W/U}, Remove a +1/+1 counter from Tawny Prophet: Scry 1, then draw a card.