After Eldrad's execution in an obliteration module was forced into a premature activation, (TV: The Hand of Fear) his remains with scattered across many worlds. Knowing that he could be restored from these fragments, King Rokon assigned Mulkris to collect them and place them in a stasis field to prevent them from restoring themselves.
Mulkris, by her own reckoning, defeated a "hundred false Eldrads" on as many planets. She tracked the eye of the Eldrad — known as the Watcher — to Earth. She used her psychic influence on Charlie Gibbs to have him bring it to her. He in turn brought Vislor Turlough under her control. They obtained the eye from Rocco, but Mulkris lost control over Gibbs after he looked at the Watcher and fell under Eldrad's influence.
Taking control of the icebreaker Alexander, she had it contained within what the Fifth Doctor labelled a "quartzberg", a huge crystalline structure. While it was in the harbour of Ambermouth, the Doctor, Nyssa and Kate Sherrin boarded the ship. Mulkris took the Doctor for an agent of Eldrad and attempted to use her psychic powers on him, only to find him immune. When the eye of Eldrad was taken by Gibbs and implanted in his forehead, Mulkris suffered a psychic seizure.
When she awoke, Mulkris found the Doctor, Nyssa and Kate examining her collected remnants of Eldrad. The Doctor tried to persuade her to destroy them, but she replied that her orders came from Kastria. The Doctor told her that the planet was desolated. Initially unwilling to believe this, she made numerous attempts to contact the homeworld and then accepted it as truth, learning that her people were dead, with only herself and Eldrad remaining.
Encountering Gibbs, Mulkris threatened him with a dart of the acid developed by Eldrad, but he turned it back, killing her. She bequeathed her genetic ring to the Doctor who left it in his TARDIS when he returned to Kastria. The energy from its power source restored her through the ring. Mulkris discovered that the Eldrad born from the eye was dead, but that restored from the hand, that the Doctor had cast into an abyss, remained. She instructed Turlough to destroy Eldrad's ring, which he and Tegan Jovanka did, before using a dart of the acid, specifically that used to kill the Eldrad of the eye, to kill that of the hand.