The colossus is an antiquated protoss war machine, dating back to the Kalath Intercession. It is a towering construct, striding 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. A colossus's beam cuts a fiery swathe of destruction through multiple enemies with each firing cycle, able to reduce a group of marines to ashes in an instant.
The colossus can be transported by the warp prism, which transforms it and other transported units into energy.
The colossus is feared for being a war machine, and some protoss believe they cannot be controlled and could turn against them.
The colossus is unique in that it was created purely as a war machine, in contrast to most protoss automatons which were mainly created for industrial and/or resource gathering purposes. Such a trait was demonstrated by the mass slaughter carried out against the kalathi, appalling the protoss. As such, the Conclave outlawed the manufacture of colossi, and existing machines were deactivated before being sealed away. Some were sent to distant asteroids and uninhabited moons. Others were stored on Aiur, some underwater, awaiting a reactivation signal. They weren't reactivated in time for the war on Aiur because it would take too long.
The war against the zerg, however, prompted the return of the colossi to the protoss arsenal. In 2503, the protoss began collecting them using coordinates collected from a preserver, despite misgivings.
In 2504, Zeratul traveled to Aiur and reactivated some colossi as part of a mission to study the body of the deceased Overmind. Later that year the Tal'darim used them as well in their defense of artifacts on Xil.
The colossus appears to step over ledges due to StarCraft II's inverse kinematics (IK) system. It can climb ledges only one level at a time and is blocked by taller cliffs. It can also step over smaller friendly units, but not other colossi or obstacles. Like other massive units, the colossus can collapse a Force Field simply by being ordered to move through it.
A colossus is tall enough to see the tops of cliffs, enabling it to climb them and fire upon the high ground without a spotter.
The colossus' height enables anti-air attacks, such as those of the missile turret, to strike it (even though it is a ground unit). Blizzard has confirmed that this is because the colossus is so tall that it counts as both a ground and air unit for the purpose of what attacks are able to hit it. If an attacking enemy unit (such as the thor) which can attack both ground and air units attacks a colossus, it will use whichever attack is stronger against the colossus.
The attack animation is a sweeping beam, with the animation taking about a second to complete. All targets continue to take damage simultaneously. The attack always strikes a linear area perpendicular to the direction the colossus is facing. This allows for a fine degree of control.
When colossi attack from a cliff, they can still be targeted by ranged units below them, unlike other ranged attackers such as the stalker.
Air units have been noted to fly through colossi, their height being ignored by game mechanics in this sense. Blizzard does not intend to change this, as shrinking the air unit would look bad and shrinking the colossus would make its ability to walk up cliffs less believable.
Colossus can have a vision of the upper ground just like the air units, while Reaper can't as a ground unit.
Colossi and Reapers can't climb up a cliff of 2 level at one time. Cydra. 2009-02-17. Cliff Climber Vision. Battle.net StarCraft II General Discussion Forum. Accessed 2009-02-18.
The Colossus will be able to see on top of cliffs, allowing it to climb up without a 'spotter.' Karune. 2008-02-13. Terran Medic Abilites. Battle.net StarCraft II General Discussion Forums. Accessed 2008-02-13.
↑The artists are still working with what would look best on the Colossus. In the latest build, many have seen that there is a beam sweeping from one side to another as the current visual.
Please also note that this is temporary art still, and even though that beam does seem to sweep randomly, it is actually doing instant damage to the whole line rather than what the visual implies, which is doing damage from one side to the other. Karune. 2008-09-09. Is the Colossus's dual-beam back?Battle.net StarCraft II General Discussion Forum. Accessed 2008-09-09.
↑The Colossus always attacks in a linear area horizontal to where the Colossus is facing. This does take a little more coordination than a Hellion or Lurker, but will no doubt still be possible at a high skill level of play. Karune. 2009-04-28. Has the Colossus changed in recent builds? (post 7)Battle.net StarCraft II General Discussion Forum. Accessed 2009-04-28.
↑Even though the beam is currently shown visually in various ways, the damage is done to all units in that straight line at the same time instantly. That line will always be based on the position you are attacking from, so in that way there is a lot of control as how to use the Colossus. Karune. 2008-10-20. Karune: Colossus. Battle.net StarCraft II General Discussion Forum. Accessed 2008-10-20.
↑ 23.023.1Colossus is Tier 3. He has a very powerful attack that strikes in a line relative to his position. He is a vital weapon against Terran infantry and Hydralisks which have become more of a threat when being protected by Roaches. Against Terrans you can go High Templar to deal with infantry, but Ghosts can really ruin that. Colossus is a safer choice.
The original attack is not coming back. The old beam was just "more damage." Simple, but not fun. The current Colossus weapon encourages micro since it really matters who you shoot and the angle you shoot them from. Fortunately since the Colossus can step up and down cliffs and over friendly units he can move to the optimal position if you are fast enough. The biggest problem he has right now is with Neural Parasite on the Infestor. It's really giving the Colossus a hard time. We are working on that today. Cavez. 2009-05-15. Regarding the most honourable Colossus. Battle.net StarCraft II General Discussion Forum. Accessed 2009-05-16.
↑It does not currently have any blind spots. On a side note, we are working to buff up the Colossus a bit more to have more burst attack (more attack damage but slower attack speed). Previously, in order for the Colossus to be very effective, a Protoss player would need several of them on the field attacking at the same time. This change should make the Colossus more effective with smaller numbers. Karune. 2009-02-03. Does the Colossus have a blind spot?Battle.net StarCraft II General Discussion Forum. Accessed 2009-02-03.