I've posted an entry on my gameblog entitled The Many Faces of Xathoqqua which details the following several custom classes for the ACKS game rules. Folks here might not be interested in the rule details, but I'd like to share some background on the worship of Xathoqqua in my home campaign:
As befits a deity of Chaos, the worship of Xathoqqua is split into several sects, the principal of which is the Xathoqquan Orthodoxy. Focusing on the Old One as the chief among Hyperborean deities, Clerics of Xathoqqua spread the faith and root out heresy.
Some servitors venerate Xathoqqua for his mystical insights. To his Sorcerer-Priests, the Old One grants antemundane secrets from the outlying planets and realms extra-dimensional.
And there are others who recognize Xathoqqua in his aspect as the Frog God. Swamp Priests and Witches conduct strange ceremonies and croak obscene rites in the night under the light of Kyranos. (Considered heretical by the Orthodoxy.)