Serpent's Tongue is the eighth episode in the eighth season of Doctor Who, set on the distant planet of Manr. It sees the first appearance of the Mara since 1983's Snakedance, and also the first appearance of the White Guardian masquerading as the Guardian of Mara since 1983's Enlightenment. It is considered the first in a three part story arc re-introducing the White Guardian, along with Phoenixfire and The Omens.