Gatekeeper Gargoyle

Flying
Gatekeeper Gargoyle enters with a +1/+1 counter on it for each Gate you control.

Glaive of the Guildpact

Equipped creature gets +1/+0 for each Gate you control and has vigilance and menace. (A creature with menace can't be blocked except by two or more creatures.)
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Gatebreaker Ram

Gatebreaker Ram gets +1/+1 for each Gate you control.
As long as you control two or more Gates, Gatebreaker Ram has vigilance and trample.

Maze's End

This land enters tapped.
{T}: Add {C}.
{3}, {T}, Return this land to its owner's hand: Search your library for a Gate card, put it onto the battlefield, then shuffle. If you control ten or more Gates with different names, you win the game.

Archway Angel

Flying
When this creature enters, you gain 2 life for each Gate you control.

Heap Gate

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{1}, {T}, Tap an untapped Gate you control: Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Open the Gates

Search your library for a basic land card or Gate card, reveal it, put it into your hand, then shuffle.

Gateway Shade

{B}: Gateway Shade gets +1/+1 until end of turn.
Tap an untapped Gate you control: Gateway Shade gets +2/+2 until end of turn.

Explore the Underdark

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.
You take the initiative.

Hold the Gates

Creatures you control get +0/+1 for each Gate you control and have vigilance.

Selesnya Guildgate

This land enters tapped.
{T}: Add {G} or {W}.

Citadel Gate

Citadel Gate enters tapped.
As Citadel Gate enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Gate Colossus

This spell costs {1} less to cast for each Gate you control.
This creature can't be blocked by creatures with power 2 or less.
Whenever a Gate you control enters, you may put this card from your graveyard on top of your library.

Basilisk Gate

{T}: Add {C}.
{2}, {T}: Target creature gets +X/+X until end of turn, where X is the number of Gates you control. Activate only as a sorcery.

Navigation Orb

{2}, {T}, Sacrifice Navigation Orb: Search your library for up to two basic land cards and/or Gate cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.