FENRIS Mechs possess advanced sensory equipment allowing them to detect weapons and narcotics, used in the same manner bomb- and drug-sniffing dogs would, and have been seen deployed alongside LOKI Mechs. A major disadvantage to FENRIS Mechs, and indeed to all mechs, is that their software programming can be hacked, altered, or overridden by an experienced hacker, and FENRIS Mechs can be turned against those they are tasked with serving.
When attacking, a FENRIS Mech will accelerate to a set speed and jump with its rear legs, bringing the target down with its front legs in an animalistic pounce-like motion. After the target is struck, they are stunned by a taser device embedded in the 'head' of the FENRIS. When a FENRIS Mech is severely damaged, the mech will deactivate and remain stationary. If shot while in this deactivated state, the mech will explode. FENRIS Mechs are deployed in packs and make a habit of 'swarming' enemy positions.
The FENRIS Mech possesses weak armor (on higher difficulties), making them relatively easy to dispatch, but are deployed in groups to counter this.
- FENRIS mechs are very weak, and Incendiary Ammo or Disruptor Ammo will bring them down quickly. They are much quicker than other mechs, however, and usually attack in groups. If priority is not given to incapacitating them at range, they can become a major threat, often disabling shields and stunning characters from behind cover; coordinated enemy squad fire can make short work of them.
- On higher difficulties such as Insanity, FENRIS mechs can take more punishment and should be taken out first, as they can quickly kill you once they are in range, especially if accompanied by other mechs.
- Biotic powers such as Throw, Pull, and Singularity are often effective at hindering the mechs, giving you time to destroy them quickly.
- The tendency of FENRIS Mechs to explode on death can be as big of a threat as their attacks, as the explosions not only deal moderate damage but can stagger you out of cover. For this reason it's even more important to take them out or at least immobilize them before they can get too close, and give them a wide berth when they die.
- FENRIS Mechs are likely named after Fenrir (also known as Fenrisulfr, meaning 'Fenris wolf'), a monstrous wolf featured in Norse mythology. Appropriately, Fenrir the wolf is the son of the god Loki.
- Sometimes when the FENRIS Mech is hacked it will stand in the same place until it is destroyed by its former ally or the hack time runs out. (Xbox 360)