The three Ultras (C: Ultraworld)
The Ultras were three humanoid aliens who acted as the custodians of Ultraworld, serving the Core. They stated their mission as the accumulation of knowledge but they also kidnapped living specimens and drained their minds, with their bodies either being fed to the Core or turned into brainless menials.
The Ultras met Avon, Tarrant and Dayna shortly after they came to Ultraworld, revealing they already knew details about them. They claimed that Cally was recovering from a mental trauma when in fact they were draining her mind. They nearly transfixed Tarrant with mental powers but were distracted when Dayna set off an explosive. They managed to capture Avon and drain him, despite him resisting. They planned to make Tarrant a menial and feed the others to the Core.
Since the human "bonding ritual" was the only omission from their knowledge of Earth culture, when Tarrant and Dayna were captured, the Ultras asked them to demonstrate, saying they would reconsider their fate if they agreed. They also confirmed that the mental drain was reversible. Tarrant and Dayna agreed but then escaped from their cell.
At the same time, the Ultras attempted to have the Core influence Vila into piloting the Liberator into Ultraworld. However, thanks to Orac's intervention, this resulted in the Core becoming unstable. In the confusion that followed, two of the Ultras were killed by Tarrant. The last Ultra disintegrated as the Core collapsed. (C: Ultraworld)