Mark of Azathoth
From Tardis Wiki, the free Doctor Who reference
The Mark of Azathoth was the supernatural branding Azathoth gave her most faithful followers.
It caused them to be transubstantiated into rakshassi and was seen by Azathoth's followers as a mark of her love and a very great honour. It was possible to hold off one's transformation for a time, though not completely, as the nails of the hands would still begin to lengthen into claws and the skin would redden and blister, all in anticipation of the full transformation. (PROSE: All-Consuming Fire)
