Priestesses and Nuns of Halone - Title?

[Kakurady]

Incidentally, the Church of Halone is the only fully established church of a member of the Twelve we've seen[...]

The Fist of Rhalgr was another organized group that worshipped one of the Twelve, but they're currently defunct-although there are still some extant members.

Going further off topic, Althyk appears to be the least mentioned of the Twelve, though the Bards of yesteryear appears to revere Him. But bards are probably as far from an organized group as you can get.