msem-instigator

Whenever another nontoken creature you control enters, create a 1/1 green Saproling creature token.
{1}{G}, {T}: Populate. (Create a token that's a copy of a creature token you control.)

Trample
When Ashka Ritualist enters or whenever you cast a spell, if {R}{W} was spent to cast it, create two 1/1 red and green Warrior creature tokens. Put a +1/+1 counter on Ashka Ritualist.

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
This creature can't be blocked by creatures with power 1 or less.

Ward—Exile three cards from your graveyard. (Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player exiles three cards from their graveyard.)
Menagerie — Astralhorn Familiar gets +2/+2 as long as there are five or more creature types among creatures you control.

Flash
When Blade of Mautakesh enters, creatures you control gain poisonous 1 until end of turn. (Whenever those creatures deal combat damage to a player, that player gets a poison counter. Multiple instances of poisonous trigger separately.)

Branch Prowler can't be blocked except by creatures with flying.

Trample
Whenever Charging Cassowary deals combat damage to a player, you may cast a copy of an Adventure of a permanent you control.

Concord — When Coralight Communer enters, if there are four or more card types among permanents you control, draw a card.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Crusher Beetle can't be blocked by more than one creature.

When Desperate Botanist enters, create a 0/1 green Plant creature token with “{T}: Add {G}.”
{5}{G}: Transform Desperate Botanist. Activate only if it's attacking.

Hexproof

{4}, {T}: Add {W}{U}{B}{R}{G}.

Trample
When Dogged Pioneer enters, create a 2/2 green Hound creature token.
Whenever a land you control enters, put a +1/+1 counter on Dogged Pioneer and up to one target Hound.

Landfall — Whenever a land you control enters, you may pay {1}{G}. If you do, create a 2/2 green Wolf creature token.

Reach

When Dylso Charmer enters, if you cast it from exile, create a 2/2 white Cat creature token.
Prophecy {1}{G} (Once each turn, you may exile a card with prophecy as you reveal it. When you do, you may cast it for its prophecy cost as long as it's exiled.)

Creatures you control enter with a +1/+1 counter on them if you spend three or more colors of mana to cast them.

Vigilance
Art of war — At the beginning of your end step, if Emperor Kenshiro dealt damage to an opponent this turn, you may put a creature card from your hand onto the battlefield tapped.

You may exert Fleetfooted Survivalist as it attacks. (An exerted creature won't untap during your next untap step.)
Whenever an exerted creature you control deals combat damage to a player, draw a card.

When Forest Whale dies, put a number of +1/+1 counters on target creature you control equal to Forest Whale's power.

Trample
Menagerie — Whenever Frondpond Fledglings attacks, if there are five or more creature types among creatures you control, put a +1/+1 counter on it.

Reach
Prismatic — Whenever you cast a multicolored spell, you gain 2 life.

{T}, Sacrifice a land: Draw a card.
When Glutton of Zhava dies, return all land cards from your graveyard to the battlefield tapped.
Foreshadow {4}{G}{G} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

When Golden Grizzly enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Rapport — Whenever Grayce Blaen and at least one other creature you control become tapped, scry 1, then reveal the top card of your library. If it's a land card, you may put it onto the battlefield tapped.