An aquatic mammal native to Atria, the poikos is a highly-prized animal among the Decheeran, who happily tend them to enjoy their rich and shimmering colors and patterns. An adult poikos resembles a large and sturdy fish with long, trailing fins and a flared, diaphanous tail that drifts beautifully in the water. It swims slowly, often letting the current carry it, with occasional bursts of wiggling energy as it thrashes to the surface when faced with the prospect of food. Its snout is extended and cylindrical like a bottle-neck, lined with small but sharp teeth. Its stout body is covered in shimmering scales that glitter in patches of orange, silver and black, while its drifting fins and tail shimmer in patches of the same colors and curl in the water like dissipating ink.

Poikos in their juvenile state are called karepoi.