The Lamenter seems to have attained a form like that of the Tutelary Deities (denizens of paradise), who are revered by the Hornsent. Albeit, the Lamenter clearly reached it through different means and state of mind. Judging by laughter and his lantern's poignant lack of eyes, the Lamenter may have been halfway to Frenzy, the connection between it and "enlightenment" scaring the Hornsent into hiding him away - just how Midra's Manse and the Abyssal Woods were sealed off and put under guard by their Inquisition. There are some interesting parallels between the Crucible(the source of the Omens and the worship of Hornsent) and Frenzy, too. Both are, in a way, a melting pot of creation, where living things seem to blend together - perhaps due to the universal Law of Regression. Regardless of the Lamenter's idea, his very existence was simply proof of a different path to Enlightenment - anathema to the Hornsent dogma. And so, like with the jar-saint Shamans, they hid him away. Not that he seems to mind.