msem-instigator

Flying, trample, haste
Dragons you control get +3/+3 as long as you control permanents with total mana value 20 or greater.
Whenever you spend five or more mana to cast a spell or activate an ability, create a 2/2 red Dragon creature token with flying.

As an additional cost to cast this spell, tap three untapped creatures you control with power 1 or less.
Search your library for a creature card, put it onto the battlefield, then shuffle.

{B}, Pay 2 life: Draw a card.

Flying, trample
When Greedstoker Demon enters, you lose X life and create X Treasure tokens, where X is your devotion to black. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)
You can't sacrifice more than one Treasure each turn.

Green spells you cast with mana value 5 or greater cost {1} less to cast.
Whenever you cast a green spell with mana value 5 or greater, draw a card.

Haste
When Greenwood Outrider enters, creatures you control gain trample and get +X/+X until end of turn, where X is the number of storied permanents you control. (Enchantments and legendary permanents are storied.)

Whenever a Hound you control is dealt damage, Greypelt Emissary deals 1 damage to any target.
Whenever Greypelt Emissary attacks, you choose how target creature blocks this combat.

Whenever another Hound you control enters, put a +1/+1 counter on Greypelt Initiate.

Enchant player
Death knell — Enchanted player loses 1 life and you gain 1 life. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
Whenever a creature you control dies, enchanted player chooses a death knell ability of a permanent you control. Trigger that ability.

Griffin Country enters with a feather counter on it.
Creatures with flying you control get +1/+1.
{U}, Remove a feather counter from Griffin Country: Put a flying counter on target creature you control.
{2}{U}, Remove a feather counter from Griffin Country: Search your library for a creature card with flying, reveal it, put it into your hand, then shuffle.

Whenever a creature dies, put a +1/+1 counter on Grim Armory.
Whenever a creature you control enters, you may move a +1/+1 counter from Grim Armory onto it.

As Grim Bastion enters, you may pay 2 life. If you don't, Grim Bastion enters tapped.
{T}, Sacrifice Grim Bastion: Search your library for a Swamp or Forest card, put it onto the battlefield, then shuffle.

When Grim Festivities enters or at beginning of your upkeep, you may return a creature card from your graveyard to the battlefield under your control. If you do, each opponent may return a creature card from their graveyard to their hand.

{B}, {T}, Exile two cards from your graveyard: Create a 1/1 white Spirit creature token with flying.

{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.”)

Whenever another nonland creature you control dies, return it to the battlefield tapped with a sapling counter on it. It becomes an Animus land named Bitter Hazel, loses all other card types, and gains “{T}: Add {G}” and “Pay this card's mana cost: This land becomes a creature until end of turn. It's still a land.”

Flash
Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
When Grim enters, if you sacrificed a permanent this turn, exile target tapped creature.

Whenever Grin, Scourge of Goresand attacks, when you next cast an instant or sorcery spell with mana value 3 or less this turn, copy that spell. You may choose new targets for the copy.
Dash {2}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Sacrifice another creature: Grindlesnap gets +3/+2 and gains trample until end of turn if that creature was a Crocodile. Otherwise, it gets +1/+1 until end of turn.
Whenever Grindlesnap is dealt combat damage, create a 3/2 green Crocodile creature token with trample.

Enchant opponent
When Grisly Hunger enters, enchanted player's life total becomes 10.
At the beginning of enchanted player's end step, they sacrifice a creature. If they do, they lose life equal to that creature's power.

Sacrifice another creature: Grisly Rougarou deals damage equal to the sacrificed creature's power to any target.

Choose two —
• Target player sacrifices a creature.
• Grixis Command deals 3 damage to target player or planeswalker and you gain 3 life.
• Return target spell to its owner's hand.
• Return target monocolored instant or sorcery card from your graveyard to your hand.

Grizzled Den enters tapped.
{T}: Add {R} or {G}.
{3}{R}{G}: Until end of turn, Grizzled Den becomes a Bear creature with trample in addition to its other types.
Scavenge {4}{R}{G}

{4}{G}{G}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
When Grizzly Matriarch becomes monstrous, destroy target noncreature permanent an opponent controls.

[+2]: Destroy up to one target noncreature permanent.
[0]: Grohl becomes a legendary green 6/6 Elk Giant creature with trample, hexproof, and haste until your next turn.
[–9]: For each permanent you control, create a token that's a copy of it.