Oculus

The Oculus is a fast-moving device used by the Reapers as a space and atmospheric superiority craft. They were first seen being used by the Collectors to protect the Collector base.

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

Oculus
Type	Synthetic
Faction	Collectors
Armament	Particle Beam Weapon
Abilities	None
Armor	Very High
Locations	Tartarus Debris Field

The Normandy SR-2 was 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 were destroyed by the Normandy's weapons or by accidentally flying into debris, one was able to penetrate the ship's hangar deck, losing its outer shell in the process. It was eventually destroyed by Commander Shepard.

It is likely that the Collectors gained the Oculus technology from the Reapers.

Jack will be killed by an Oculus' particle beam unless Shepard upgrades the Normandy SR-2 with Heavy Ship Armor.

Capabilities

Offensive

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.

Defensive

The Oculus has an incredibly strong armor, which acts as its health.

Tactics

• The battle with the Oculus occurs in two phases with a cutcene in between. In both phases, it will slowly advance and attempt to take a clear shot with its particle beam.
• In the first phase of the battle, you only need to lower its armor to about 50% of its "health", and it will retreat. During this first phase, the Oculus will ignore your squadmates and focus exclusively on Shepard, but you can safely remain behind the control console that you encounter as soon as you enter the shuttle bay: the Oculus will not move behind the console to flank you. Remain in cover while it is firing, then pop up and take it out. After the cutscene, an Oculus will invade the ship again, and you'll have to fight it to the death.
• In the second phase of the battle, you will start at the opposite end of the shuttle bay from before, so you will need to find different cover. Also, even if you manage to return to your spot behind the control panel the Oculus will now fly right across it to flank you. There are several tall solid objects running lengthwise down the main area which you can use for cover, and you can dodge around them when the Oculus attempts to flank you, always interposing them between yourself and the Oculus. The Oculus will chase Shepard to begin with, but after being damaged and dodging out the holes in the side of the Normandy a time or two it will tend to start chasing your squadmates instead, making your job a lot easier.
• Shooting the red "eye" will cause more damage than shooting the silver shell.
• Explosive heavy weapons (such as the ML-77 Missile Launcher or M-100 Grenade Launcher) are quite effective, however, using M-920 Cain is not recommended as its explosion can easily kill you. The Collector Particle Beam and M-451 Firestorm are effective as well, however, you are highly exposed to the Oculus' own particle beam, which is not recommended on higher difficulties. Such powers 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. 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 three "shield" powers (Geth Shield Boost, Fortification, and Barrier) are immensely helpful in protecting yourself while fighting the Oculus. Wait until the Oculus is just about to clear your cover, activate the power, and sprint to the other side of the room. If timed correctly, the extra shielding from a maxed-out boost can protect you out in the open all the way to the other side, and the power will be available to you the next time the Oculus reaches your position.
• The Oculus is unaffected by Stasis.
• Using Tactical Cloak as an Infiltrator does not stop the Oculus from its relentless pursuit of the player, but it will still provide the damage bonus it always provides when you fire.
• At least two sets of Power Cells can be found about the shuttle bay. As usual these will resupply ammo for all of your regular weapons as well as your heavy weapon.

Mass Effect 3

The Oculus returns in Mass Effect 3, serving as an atmospheric and exoatmospheric fighter and interceptor for Reaper forces. Several Oculi can be seen during the first mission 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. The Oculus is seen only in cutscenes or in the background of various levels, and cannot be engaged in combat as in Mass Effect 2.

Trivia

• Oculus is Latin for 'eye'.
• True to their name, Oculi can see through both the Normandy SR-2's stealth systems and an Infiltrator's Tactical Cloak.
• 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.