Extradimensionals.

These are creatures first seen in REALM 5. They are allied with Sokar and appear to consist of some sort of bulletproof rock; even the weakest ones are much more powerful than most humans, as during REALM 5 they were shown effortlessly defeating AAHW troops who had superior equipment. They are mostly found in a type of underworld that apparently exists below the uppermost part of the Earth's crust (or possibly a portal to it????????????? idk lol). Evidence of their existence was not shown until REALM 5, hence the episode's name "Revelation". There are multiple types.
Type 1 (Insert names here please because I am very uncreative): This is the weakest extradimensional type. They appear to be grunts with slightly hunched backs and torn shirts. Their mouth is filled with sharp teeth that appear to be made of the same rock. They are more agile than humans and can cling to surfaces. They are fearless and they attack aggressively. They are usually unarmed, but sometimes they carry swords which are likely made of a material from the same dimension. This material is quite strong as it can withstand hits from Kelzad's chargers. These types of extradimensionsals, although not as disposable as AAHW troops, are defeated by Kelzad without the latter sustaining any serious damage. Kelzad even managed to throw one into a void and rip another's upper head off with his bare hands.
Type 2: This type appears to be a direct upgrade of the first type like agents are an upgrade of grunts. These monsters have a more curved back that is deformed similarly to Yeelon's back. They are much faster, more aggressive, and more damage-resistant than type 1s. One was split in two by Kelzad's chargers but it survived and had to be finished off. A second one managed to dodge all of Kelzad's MP9 bullets, forcing him to engage the type 2 with his charger once more. This type was never seen engaging the AAHW on the Earth, only fighting Kelzad in the alternate dimension.