Oculi are cybernetic constructs, being piloted (in the case of those used by the Collectors) by a single Collector drone. Each drone is stripped down until only its nervous system remains, with the remaining tissue hardened to withstand vacuum and integration into an Oculus shell.
Oculi possess powerful beam weapons, similar to other Reaper and Collector weaponry, and can invade an enemy ship by cutting into its hull after jettisoning part of its armor.
Mass Effect 2
The Normandy SR-2 is attacked by several Oculi when attempting to reach the Collector Base. The Oculi were apparently left on guard in the local debris field and only activated as the Normandy approached. While most of the Oculi are destroyed by the Normandy's weapons or by accidentally flying into debris, one is able to penetrate the ship's hangar deck, losing its outer shell in the process. It is eventually destroyed by Commander Shepard.
It is likely that the Collectors gained the Oculus technology from the Reapers.
The Oculus' beam weapon is much stronger than an ordinary particle beam, and will blast away any shields or barriers in a moment, especially on higher difficulties. It fires its weapon in very long bursts, thus anything longer than a brief exposure to this weapon could be fatal.
The Oculus has an incredibly strong armor, which acts as its health.
- Shooting the red "eye" causes more damage than shooting the silver shell.
- Standard weapons with high armor damage bonuses (such as the M-98 Widow, M-92 Mantis, M-5 Phalanx or M-6 Carnifex) are effective, if a little time consuming and dangerous. Your squad will continually comment that it will take heavy weapons to succeed, but it can be done with pistols if that's the way you want to go.
- The ML-77 Missile Launcher or M-100 Grenade Launcher can be risky as they cause friendly fire damage and the numerous explosive crates and canisters in the cargo bay can be set off causing an additional hazard to Shepard's team. The Missile Launcher is fairly effective as it does not require any line of sight and the missiles will automatically home in on the Oculus regardless of where they are fired as it is the only enemy target.
- The M-920 Cain is time-efficient but extremely risky as its explosion can easily kill you in close proximity.
- The Collector Particle Beam and M-451 Firestorm do high damage, but you are highly exposed to the Oculus' own particle beam, which is not recommended on higher difficulties.
- Heavy weapon ammo will be completely refilled to 100% capacity at the start of the next mission (along with medi-gel), and there are also power cells that can be picked up around the cargo bay so conserving ammunition isn't a concern.
- Powers such as Incinerate, Warp, Reave and/or Incendiary Ammo are very good in stripping away its armor. Most biotic powers (except for Warp and Reave) are ineffective. Incinerate and Warp are especially useful as they can arc around cover minimizing exposure.
- The three "shield" powers (Geth Shield Boost, Fortification, and Barrier) are immensely helpful in protecting yourself while fighting the Oculus, especially during brief moments you are open to its fire when changing cover locations.
- The Oculus is unaffected by Stasis.
- The Oculus can see through Tactical Cloak and will target Shepard even while cloaked, making the power only useful for its damage boost.
- The Oculus remains single-mindedly focused on Shepard during the initial stages of the fight, but eventually will switch targets to your squadmates. When this happens it can be very difficult to keep them alive, but as noted above medi-gel will be freely refilled following the fight so just revive them.
- While the Oculus remains focused on you, it can be a good idea to explicitly order your squadmates out of cover into the open as far away from you as possible to prevent them from getting in your way as you carefully hug cover to prevent exposure to the particle beam. They won't be in danger until the fight progresses to where the Oculus decides to fry them instead.
Mass Effect 3
Oculi are deployed en masse by the Reapers during their 2186 invasion, serving as atmospheric and exoatmospheric fighters and interceptors. Several Oculi can be seen during the initial attack on Earth, attacking Alliance fighters and A-61 Mantis Gunships. Squadrons are also seen in action over Palaven and later during the battle to retake Earth.
No Oculus directly engaged Shepard during the war, in contrast to the Normandy incursion earlier.
- Oculus is Latin for 'eye'.
- The center of a Destroyer's primary beam weapon is identical to an Oculus.
- The Oculus' design was based on a stereo speaker, and the reference for the eye was HAL 9000.
- The Art of the Mass Effect Universe