In the upcoming Gears of War Book, Gears of War: Anvil Gate, the Lambent invade the surface of Sera. In Gears of War 3, they have been confirmed to be the main antagonists.
Polyp
The most basic form is known as a Lambent Polyp, which has a crab-like appearance is normally spewed from Lambent hosts after they have been destroyed.
Stalk
Lambent Stalks are huge plantlike tentacles that swarm over battle sites, dropping other Lambent forms into their enemies midst. These are massive, and easily identifiable from the smaller mutation of the Lambent Drudges. The opening level of Gears 3 involves Lambent Stalks rising out of the ocean, dropping other Lambent into the Raven's Nest.
Drudge
The Lambent Drudge, hideously mutated Locust Drones, are the most recognizable part of the Lambent's fighting force. However, these creatures have lost all forms of sentience seen in the Lambent Drones that attacked the Locust city of Nexus. They have the ability to morph their ligaments and heads, forcing its enemies to constantly change tactics and becoming an even deadlier threat.
Lambent Wretch
Lambent Wretches are one of only three encountered Lambent-infected Locust. Delta Squad ran into several of them in the Imulsion Factory on Jacinto Plateau. It is likely they are amongst the Lambent that invade the surface of Sera 18 months after the sinking of Jacinto.
Lambent Drone
Lambent Drones are Drones that have been exposed to Imulsion enough to become Lambent but not long enough to mutate into Drudges. Lambent Drones essentially share the same appearance to their Locust counterparts with the exception of their glowing skin, at least the ones Delta Squad encountered in Nexus did. During the Lambent Invasion the Drones have a slightly different appearance, similar to a combination of the Drones encountered in Nexus and the Drudges, thus hinting that Drudges are the next stage in a Drone's mutation.
Lambent Brumak
The Lambent Brumak is the largest known Lambent creature. They are at least double the size of a regular Brumak, sporting large, snapping tentacles it is barely recognizable once its mutation is complete.