Taurean Mauler

Changeling (This card is every creature type.)
Whenever an opponent casts a spell, you may put a +1/+1 counter on Taurean Mauler.

Sunrise Sovereign

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

Mountain

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.

Blind-Spot Giant

Blind-Spot Giant can't attack or block unless you control another Giant.

Thundercloud Shaman

When Thundercloud Shaman enters the battlefield, it deals damage equal to the number of Giants you control to each non-Giant creature.

Vivid Crag

Vivid Crag enters the battlefield tapped with two charge counters on it.
{T}: Add {R}.
{T}, Remove a charge counter from Vivid Crag: Add one mana of any color.

Avian Changeling

Changeling (This card is every creature type.)
Flying

Plains

War-Spike Changeling

Changeling (This card is every creature type.)
{R}: War-Spike Changeling gains first strike until end of turn.

Kithkin Greatheart

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

Lowland Oaf

{T}: Target Goblin creature you control gets +1/+0 and gains flying until end of turn. Sacrifice that creature at the beginning of the next end step.