The House of Light is the religious organization (or organizations) devoted to the worship of the Gods Above, usually preaching from the Book of All Things and providing Light-healing as a service to everybody in need.
Priests trained by the House of Light are capable of wielding the power of Light for healing or several other purposes, like creating shields or rays of light in battle.
Callow's House of Light is noted to be old-fashioned by Procerans and tend to keep out of worldly politics.
The House of Light in Callow suffered a split following the naming of Catherine Foundling as the Arch-Heretic of the East in Procer, sparking the rise of the House Insurgent in Callow, who provide their services to the Army of Callow. The traditional House of Light is called House Constant.
House Insurgent trades high-end healing with a more aggressive use of Light. It has been noted that priests generally have to choose if they wan't to be good at healing or good at more combative uses of Light.
The House of Light in Procer has a much more organized approach to things than their sister-organization in Callow.
During Roland's backstory we learn of a local Proceran priest that uses their power to deny people healing unless they follow the priests demands. Something that didn't seem to shock anyone.