Fertilid

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

Plains

Golden-Tail Trainer

Aura and Equipment spells you cast cost {X} less to cast, where X is Golden-Tail Trainer's power.
Whenever Golden-Tail Trainer attacks, other modified creatures you control get +X/+X until end of turn, where X is Golden-Tail Trainer's power. (Equipment, Auras you control, and counters are modifications.)

Envoy of the Ancestors

Outlast {W} ({W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Modified creatures you control have lifelink. (Equipment, Auras you control, and counters are modifications.)

Guardian Gladewalker

Changeling (This card is every creature type.)
When Guardian Gladewalker enters, put a +1/+1 counter on target creature.

Nyxborn Hydra

Bestow {X}{G}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
Reach, trample
Nyxborn Hydra enters with X +1/+1 counters on it.
Enchanted creature gets +1/+1 for each +1/+1 counter on Nyxborn Hydra and has reach and trample.

Forest

Faithful Watchdog

Vigilance
Faithful Watchdog enters with three +1/+1 counters on it.

Metastatic Evangel

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

Glyph Elemental

Bestow {1}{W} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
Landfall — Whenever a land you control enters, put a +1/+1 counter on Glyph Elemental.
Enchanted creature gets +1/+1 for each +1/+1 counter on Glyph Elemental.

Dauntless Survivor

When Dauntless Survivor enters, put a +1/+1 counter on target creature.

Codespell Cleric

Vigilance
When Codespell Cleric enters, if it was the second spell you cast this turn, put a +1/+1 counter on target creature.