msem-instigator

Granite Sibyl enters with three +1/+1 counters on it.
Whenever another creature you control enters, move a +1/+1 counter from Granite Sibyl to that creature.

Reach

When Grave Reaper enters, if it wasn't cast from your hand, it gets +1/+1 until end of turn.
Unearth {B} ({B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

You may have Graveborn Usurper enter as a copy of any creature card in a graveyard, except it has “{2}{U}{B}, Exile a creature card from a graveyard: Graveborn Usurper becomes a copy of the exiled card, except it has this ability.”

Destroy target creature. If you control a Wizard, put up to one target creature card from your graveyard on top of your library.

Whenever Green Pelt Hart or another Elk creature you control deals combat damage to a player, draw that many cards.

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Griffin Skycaller enters, target creature you control gets +1/+1 and gains flying until end of turn.

Target player sacrifices a creature. Create a tapped 2/2 black Zombie creature token.

{T}, Pay 1 life: Add {B} or {R}.
{1}, {T}, Sacrifice Grim Slums: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Put target creature on top of its owner's library.

Grisly Marsh enters tapped unless another player controls a land that could produce {B} or {G}.
{T}: Add {B} or {G}.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
When Grizzled Captain becomes renowned, create two 1/1 white Soldier creature tokens.

Defender (This creature can't attack.)
Adorned — Grouchy Warden gets +2/+3 as long as it's equipped and/or enchanted.

Create two 1/1 red Goblin creature tokens.

Enchant creature
Enchanted creature gets +3/+3 and has trample.

When Guardian of the Wurm enters, create a 6/6 green Wurm creature token with trample.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Whenever a creature you control attacks alone, target creature an opponent controls blocks this turn if able.

You may put a green creature card from your hand onto the battlefield. If you do, it fights target creature you don't control.

Hexproof, trample
Whenever Gui, the Islandbringer deals combat damage to an opponent, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put it into your hand.

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets +2/+1 and has trample.

Target creature gets -3/-3 until end of turn. When that creature dies this turn, its controller loses 2 life.

When Gulch Glutton enters, create a 1/1 black Rat creature token.
Whenever Gulch Glutton perseveres, each player sacrifices a creature. (A creature perseveres when it survives damage.)

When Gusma's Artisan enters, search your library for a card, then shuffle and put that card on the bottom of it.
{2}{U}, Sacrifice Gusma's Artisan: Manifest the bottom card of your library. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Prowess
Gusma's Emissary gets +1/+1 as long as you control a black or green permanent.