Searing Light

Searing Light are supernatural hunting dogs of the Heavens, tasked with extermination of the enemies of the High Gods. Unlike the more defensive Unbroken Host (whose main job is assistance of the believers), the Light is the relentless attack force. Servants of the Light will rarely assist the mortals, instead preferring to directly assault the strongholds of the Hierarchs in the Lost Lands and send supernatural death squads after certain, handpicked types of mundane offenders.
Searing Light goes after mortals attempting to mess with time and trying to - in any way - alter their souls. Those who do that and fail to hide their tracks properly will almost certainly get visited by the Light’s death squad and promptly exterminated. Other than that, it mostly avoids contact with mortals, unless they happen to be collateral damage during its campaigns against the spirits serving the Fallen Gods.
Majority of the Light’s forces are busy fighting their war among the Spiritual and Radiant Worlds, but they still maintain a number of permanent holdouts within the Lost Lands. As a result, they are occasionally seen by the imperials as one more of many groups fighting for supremacy over them, just one that leaves the mortals alone unless they worship the Hierarchs.
The biggest of the Light’s contributions for the Empire’s defense is the Solar Blessing - the supernatural effect that actively weakens all hostile supernaturals during the day, with damage growing progressively the closer it is to noon. There are ways of suppressing that effect (typically requiring an archdaemon or a demigod around), but as a whole, it’s a massive weakness of the enemies of the Grand Empire. Unfortunately, it only works outside of the Lost Lands and in the direct neighbourhood of the Light’s strongholds in them.

Territories

Sky Haven - The Spiritual World of celestial fortresses and cities floating among the skies, with no ground to speak of. It is the main stronghold of the Searing Light in the multiversal ‘neighbourhood’ of the Prime Material World, known (among many other things) to house massive prison complexes where untold number of spirits in thrall of the Fallen Gods (and even some lesser deities) are imprisoned.
The prisoners are - according to theology - awaiting their final judgment when the war between the gods comes to an end. In the meantime, they are kept outside of the battlefields by legions of fanatical wardens.

Military

Purifiers - An entire host of humanoid warriors (with the metallic wings on their backs that allow them to fly or float around). They aren’t one of the Dead, as the Searing Light prefers to not rely on them, seeing them as inherently corruptible.
Purifiers are powerful, but have a tendency to be too specialized for their own good. Their attacks deal incredible damages to creatures considered impure by the Imperial Religion - so servants of the fallen gods, and select extrareligious threats such as Umbral Bond.
However against more mundane threats, they struggle - even a bunch of bandits can put up a decent fight against them. That’s mostly because Sol doesn’t want them to hunt such targets - she leaves their judgment to other gods, while focusing on her war.
Rainbow Fauna - The Sol is known for her enjoyment of rather wild colours. This is best pictured by a variety of ‘natural’ creatures inhabiting the Sky Haven, the Spiritual World of the Light that is best known to inhabitants of this universe.
Due to it lacking ‘ground’, all the creatures are either winged or can float in some way. Their colours are blinding, and some - such as a dreaded rainbow dragon - are not only extremely dangerous but can also weaponize the power of Sol. While summarizing their main attacks as ‘rainbow lasers’ makes them sound pitiful and weird, they are anything but. In fact, very few creatures of the Fallen can withstand a direct blast from one of those.
Naturally, many of the veteran Purifiers can occasionally be seen riding creatures of Sky Haven, some even the dreaded dragons of that place.

Religion

The one and only deity of the Searing Light is the Sol, the Exarch of Day. A most vengeful of exarchs, who, in fact, is speculated by some scholars to have Fallen, yet in way that makes her useful to the grander goals of Honor, the Exarch of Authority. She is the high god of sun, light, order and purity, who is absolutely relentless in her persecution of the impure, however is still reined in enough by the other gods to not go after those less impure (for example many speculate that her lack of interest in mundane evils is due to the Honor and Iudex seeing that as violation of their domains.
The counterargument for the 'Sol has fallen' theory is the fact that there is no form of corruption associated with the worship of Sol. Some scholars however see the notable spike in fanaticism for the devotees of Sol as being a sign of a particularly mild corruption, one that is weak enough to not be noticed by most.