Mountain

Brion Stoutarm

Lifelink
{R}, {T}, Sacrifice another creature: Brion Stoutarm deals damage equal to the sacrificed creature's power to target player or planeswalker.

Squash

This spell costs {3} less to cast if you control a Giant.
Squash deals 6 damage to target creature or planeswalker.

Stinkdrinker Daredevil

Giant spells you cast cost {2} less to cast.

Boldwyr Heavyweights

Trample
When Boldwyr Heavyweights enters the battlefield, each opponent may search their library for a creature card and put it onto the battlefield. Then each player who searched their library this way shuffles.

Ancient Amphitheater

As Ancient Amphitheater enters the battlefield, you may reveal a Giant card from your hand. If you don't, Ancient Amphitheater enters the battlefield tapped.
{T}: Add {R} or {W}.

Fire Giant's Fury

Target Giant you control gets +2/+2 and gains trample until end of turn. Whenever it deals combat damage to a player this turn, exile that many cards from the top of your library. Until the end of your next turn, you may play those cards.

Calamity Bearer

If a Giant source you control would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Kithkin Greatheart

As long as you control a Giant, Kithkin Greatheart gets +1/+1 and has first strike.

Cast Off

Destroy all non-Giant creatures. (Then exile this card. You may cast the creature later from exile.)

Realm-Cloaked Giant

Realm-Cloaked Giant // Cast Off

Borderland Behemoth

Trample
Borderland Behemoth gets +4/+4 for each other Giant you control.

Stomp

Damage can't be prevented this turn. Stomp deals 2 damage to any target.

Bonecrusher Giant

Whenever Bonecrusher Giant becomes the target of a spell, Bonecrusher Giant deals 2 damage to that spell's controller.

Bonecrusher Giant // Stomp

Clifftop Retreat

Clifftop Retreat enters the battlefield tapped unless you control a Mountain or a Plains.
{T}: Add {R} or {W}.

Sunrise Sovereign

Other Giant creatures you control get +2/+2 and have trample.

Wandering Graybeard

Kinship — At the beginning of your upkeep, you may look at the top card of your library. If it shares a creature type with Wandering Graybeard, you may reveal it. If you do, you gain 4 life.

Surtland Flinger

Whenever Surtland Flinger attacks, you may sacrifice another creature. When you do, Surtland Flinger deals damage equal to the sacrificed creature's power to any target. If the sacrificed creature was a Giant, Surtland Flinger deals twice that much damage instead.

Favor of the Mighty

Each creature with the highest mana value has protection from all colors.

Giant Harbinger

When Giant Harbinger enters the battlefield, you may search your library for a Giant card, reveal it, then shuffle and put that card on top.

Hamletback Goliath

Whenever another creature enters the battlefield, you may put X +1/+1 counters on Hamletback Goliath, where X is that creature's power.