Ohica was a priestess of the Sisterhood of Karn. She helped the Fourth Doctor destroy Morbius. She served Maren until Maren's death, then took on the role of High Priestess. (TV: The Brain of Morbius)
One of the first things Ohica did as the High Priestess was have what was left of Morbius' brain recovered. She led the wounded Morbius to the Death Zone to use the remains of Rassilon to give Morbius immortality.
At this time, Ohica discovered that Iris Wildthyme had infiltrated the Sisterhood and used the Time Scoop to bring seven of Iris' incarnations to Death Zone. She also used the Time Scoop to bring Ice Warriors, Ogrons, Sea Devils, Zarbi, Mechanoids, and Quarks to the Death Zone to kill the Irises. The Irises got past the monsters and were able to stop Ohica's plot. (PROSE: Verdigris)