msem-instigator

As Game Trail enters, you may reveal a Mountain or Forest card from your hand. If you don't, Game Trail enters tapped.
{T}: Add {R} or {G}.

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Gamhaugen Burns deals 3 damage to any target.

(Transform this if it's not attached to a creature. Pay {R} as a sorcery to unattach it.)
Enchant creature you control
Gamhaugen War Swine's rider gets +1/+1 and has haste.

Ganzorig's Domain enters tapped.
When Ganzorig's Domain enters, you may mill two cards.
{T}: Add {R} or {G}.

Flash

Trample
Cycling {2} ({2}, Discard this card: Draw a card.)

Once each turn, when you cast a creature spell, you may copy it for each other spell you cast this turn. (A copy of a creature spell becomes a token.)
Whenever Garragrok, Horde Tyrant attacks, add {R}{R}{G}{G}. Until end of turn, you don't lose this mana as steps and phases end.

Creatures you control can't be blocked by creature tokens and/or creatures with defender.
At the beginning of your end step, if Garrison Intruder didn't attack this turn, transform it.

{2}{G}, Sacrifice a land: Gashing Panther gains indestructible until end of turn. Tap it.

{1}, Sacrifice Gasoline Canister: It deals 1 damage to any target. If a creature or planeswalker dealt damage this way would die this turn, exile it instead.

When Gate of Realms enters, you may search your library for a land card, reveal it, and put that card into your hand. If you do, shuffle.
{10}, {T}: Gate of Realms deals 3 damage to any target. This ability costs {1} less to activate for each different name among lands you control.

{T}, Pay 2 life: Add {B}.
{T}: Add one mana of any color. Spend this mana only to cast spells from your graveyard or activate abilities of cards in your graveyard.

When Gateway Statues enters, put a +1/+1 counter on target creature you control.
{T}: Add one mana of any color.

At the beginning of your end step, amass Soldiers 1. (Put a +1/+1 counter on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

Choose a creature type. Reveal cards from the top of your library until you reveal a card of the chosen type. Put that card into your hand and the rest on the bottom of your library in a random order.

Gathering Beacon enters tapped.
{T}: Add {G}.
{2}, {T}, Sacrifice Gathering Beacon: Choose a creature or planeswalker type, then reveal the top five cards of your library. You may put a card of the chosen type into your hand, then put the rest on the bottom in any order.

Trample
Whenever Gavony Cavaliers enters or attacks, create a Weapon token. (It's an Equipment artifact with “Equipped creature gets +1/+1” and equip {2}.)
Creatures you control that are enchanted or equipped have trample.

Search your library for three land cards with different names, reveal them, then shuffle. Put one of those cards onto the battlefield, one into your hand, and one into your graveyard.

Flying
{1}, Sacrifice Gearcraft Observer: Look at target player's hand. Draw a card.

When Gemcrusher Turtle enters, choose one —
• Destroy target artifact.
• Gemcrusher Turtle fights up to one target creature.

When you cast a creature spell, sacrifice Gemini Cast. If you do, create a token that's a copy of that spell, except the token isn't legendary.

When Gemplate Golem enters or dies, put a +1/+1 counter on target creature you control.

Whenever you cast a spell with mana value 5 or greater, create an X/1 red Mutant creature token with trample and haste, where X is that spell's mana value. Exile that token at the beginning of the next end step.

When GenTech Architect enters, create a Function token with “Put two +1/+1 counters on a creature you control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

When GenTech Assistants enters, create an X/X green Mutant creature token.