Ancestor worship is the practice of worshipping ones deceased ancestors (or other exemplary members of ones race). It became widespread in the late Age of Settlement, but has suffered somewhat of a fall in popularity since the Age of Cataclysm (revealing the Elder Dragons), and more since the Revenant Crisis in the Age of Reclamation. The advent of the New Gods also gives a safer form of worship along the same lines.
Most heavily in the detraction of Ancestor Worship is the creation of incredibly powerful Revenants, by channelling ether to their soul forms in the form of Divine Magic. Although with Kalas now sending souls through Hallows Gate, this has less potential to occur if the soul was not forcibly attempting to remain.
The practise of Ancestor Worship is still very common amongst the Tel-Kabal, though they do not produce Revenants. Other practitioners of it are found most heavily amongst Aergosians, Khazadryn, Idryllian Yveralisyr, and Wilderlander Clanfolk.