|Fantasy game art from Dragon Age: Origins Ultimate Edition (Dragon Age: Origins, the Awakening expansion, and all official Downloadable Content).
Halla are snowy white deer with vine-line curly horns. They are domesticated by the Dalish Elves as beasts of burden.
From Codex entry: Halla:
No creature is more revered by the Dalish than the halla. No other animal has a god of its own. These white stags are much larger than ordinary deer, and the Dalish halla keepers carve their antlers as they grow, making them curve into intricate designs. In ancient times, these stags bore elven knights into combat, but since the fall of the Dales, they are used less as mounts and more to pull the aravels.