The colossus is a protoss robot design dating back to the bloody conflicts of the Kalath Intercession. It strides across the battlefield on four tall, slender legs which give it an extremely high level of mobility. The great height of the machine allows it to step up and down cliffs and other steep elevations with little difficulty, and gives it a dominating field of fire.

The heavily armored hull of the colossus carries two powerful thermal lances: one mounted on each side of its body. Complex focusing and targeting systems are used to pinpoint the continuous damage output of the thermal lances for optimal efficiency. As a target is destroyed, the lances are switched to a new target instantly so that a colossus' beam cuts a fiery swathe of destruction through multiple enemies with each firing cycle.