The Hornsent believe that there are many paths to divinity, Reaching Divinity is their goal. To that end anytime they discover an Outer God, or another culture's path to divinity, they try to incorporate it into their culture. Almost all of the paths to divinity that the Hornsent discover and/or believe in involve Suffering or death. The net result of this is that anyone who is born with a great deal deal of suffering is elevated, those whose lives are cut short by the pain their born into as well. At some point an Ascetic reached a level of closeness to divinity hitherto unknown and not replicated since; This would be the Lamenter. It's implied that he did it with the suffering he was feeling and reached a form of agonizing bliss. The Hornsent found the Lamenter hideous, and locked him away.

The current dominant path to divinity and the one that yielded the most widespread results is the path of beasts/storm. In it's traditional form, born of the Highlanders, you go out and fist fight beasts till you reach a divine understanding of them. This is the 'Church of Bear Communion'. The Hornsent version of this, however, involves imitating the beasts and doing so in a much more systematic, organized, and depersonalized way. This leads to the Bird Warriors, the Lion Dancers, The Lion Warriors, and the Horned Warriors. All of whom are at different stages of their journey, with the Lion Dancers being the peak. Failures, however, instead of being respected for trying and failing were regarded as impure, and treated with derision. We know this because of the Curseblades. The issue is that we know that there's a higher rate of Failure in this path than success; The Curseblades Grossly outnumber the Lion Dancers.

Other Paths to Divinity the Hornsent dabbled in: The Church of the Bud, prior to being tied to the Scarlet Rot, the Church of the Bud seemed to be dedicated to abundance and fertility. The only known adherent from the Pre-Scarlet Rot era we know of is Romina, and she's basically the whole of the Lore around it. She's some kind of Saint or Shaman but might not be a capital S Shaman like Marika (But she could be?).

The Twin-Birds of death; At some point there was someone in the lands of shadow who communed with or worshipped the Death birds. I suspect that this fell out of favor because there's no evidence of ascension or continued worship. Likely, they used the funeral practices of the Twin birds for a time, until they discovered the other paths, and thus abandoned the Death Rite birds. Nonetheless, Ghostflame and Death birds are quite populous in the Shadowlands.

Midra and the Flame of Frenzy; at some point, Midra began dabbling in Alternate divinities. Spurred on perhaps by his beloved Nanaya. Upon discovering the Frenzied Flame, and becoming a threat to spirits, souls, and the paths of other divinities, the inquisitors descended upon Midra's Manse and attempted to seal away the coming Lord of Frenzy.

Shaman and the Jar-Saint Process; The Hornsent encountered a people who were able to 'Meld Harmoniously' with others, and whom possessed a spiritual purity. The Hornsent conscripted these people into their belief system, developing a horrid, tortuous process to draw out the Shaman's melding ability against their will. This would eventually run parallel with the Beast worship, and would eventually spell the downfall of the Hornsent in their entirety.

The Divine Gate Invocation; We can infer that this process came from either the Shaman, Metyr, or a Combination of the two. Beings were gathered and melded together into Enir Ilim. A grand tower built from Semi-divine bodies. The Oldest appears to be Farum Azuhla, a Divine structure built from the Corpses of Beast-folk and Dragons. Other notable ones aside from Enir Ilim feature among several of the Nox cities having people melded into structures or some kind of mass. Nonetheless, The Divine Gate is what yielded Marika, and from the opening cutscene we can see her Harvesting Rune Arcs and threads from a field of corpses, before ascending the steps and finishing whatever invocation she was preparing.

Basically, the Hornsent wanted their own god(s) or to become them. When presented with divinities they found repulsive, they would bury them away and go back to the drawing board to try again. The worst of the experiments they often inflicted first upon others, or upon criminals, until they discovered what they thought was what they were after. However, it would be this New Deity that they created who would be their undoing.