She is portrayed by Geraldine McEwan.
Mortianna is a mysterious witch who dwells in a dungeon-like chamber within Nottingham Castle. She is the mother of the Sheriff of Nottingham, though he is unaware of this for much of the story, and she continuously spies on him through a small peephole concealed in the wall. Mortianna tends to mix various substances including her own blood and saliva in order to gain answers to puzzling situations. During one of her visions, she foresaw the death of her son and herself at the hands of Robin and Azeem respectively. This vision made her very afraid of the "painted man."
When Maid Marian is forced to marry the Sheriff, Mortianna is present during the ceremony and she attacks Robin Hood's sidekick, Azeem, when he attempts to break down the door. Azeem manages to impale her on her own spear but she quickly runs off down a corridor with the spear still embedded in her, presumably to her death. However, after Robin kills the Sheriff, Mortianna suddenly appears and attempts to kill him. Azeem rushes into the room and hurls his scimitar sword straight into Mortianna's chest, sending her flying backwards where she promptly dies.