The Seeker was an an artificial intelligence serving Anubis. She controlled a pyramid-shaped spaceship and could create a mummy-like body for herself. The Seeker called herself and Dorothy Bell the "sisters of Osiris", the last two of many.
During Anubis's millennia-long sleep, the Seeker had been tasked with seeking out all remaining Osiran devices. The non-sentient devices were to be destroyed. Her last assignment before waking Anubis was to find the last sentient Osiran device, the Architect's great key and deliver her to Anubis. When the Seeker detected the energy signatures of Dorothy, who had merged with the key, she left Anubis's ship, the Shining Horizon, travelled to Earth and tried to find the key. By mistake she transmatted Hanif, Erik Ulfriksson, the Tenth Doctor, Cleopatra Hunsicker and Cindy Wu to her ship instead of Dorothy, who camouflaged herself from the Seeker. She then transmitted an ultimatum to all Earth primates. She would destroy the planet, unless the Architect's great key was delivered to her. Dorothy saved the planet by voluntarily uncloaking herself and agreeing to surrender. The Seeker transported her and Gabby Gonzalez to her ship. Deeming all but the Doctor and Cindy to be potentially of value to the historical records, the Seeker transmatted the two back to Earth and, with the rest departed to Anubis's ship, the Shining Horizon, where she woke Anubis from hibernation. (COMIC: Spiral Staircase)
When Erik interfered with Anubis's rejuvenation on board the Shining Horizon, Seeker delivered a fatal blow which killed Hanif, who sacrificed himself for his lover.
At Anubis's orders, Seeker initiated the ascendance through the Circle of Transcendence and detected growing misalignments. Eventually, the Doctor and Dorothy persuaded Anubis to order Seeker to abort the protocol. (COMIC: Sins of the Father)
The Seeker's physical form was killed by Anubis, who had been possessed by Sutekh. This did not kill her completely, as her actual form was located in the central core of the Shining Horizon. She helped Gabby escape the central core. She also helped revive the Tenth Doctor after Dorothy Bell defeated Sutekh. (COMIC: Old Girl)