The Ritual of the Darkenwood, or the Rite of Darkening as it is sometimes called, was performed in 279 AF by Xandor and Orina, orderheads of Twilight and Demeter, in an effort to protect the forests of Sapience from the evils that plagued it under the hand of Sartan.
As a result of this ritual, the Darkenwood was brought into being, as well as the arachnoi who inhabit it.