Sithaer is the Atheran concept of hell. Dharkaron Avenger transports guilty souls here to face judgement upon death, in a flying chariot pulled by the Five Horses of Sithaer. According to Ath's adepts, Sithaer is "that state of being where the prime vibration is not recognized".
Sithaer is a human-concept, not a Paravian one. Before the formation of the Alliance of Light, Sithaer commonly appears in human oaths and epithets, such as "Damn t'Sithaer", and "Sithaer's furies".