The Orrovix were a large animalistic clawed species who fed on temporal energy. Orrovix hunted in packs, using breaks in time to their advantage. (AUDIO: Nevernor)
History
The Orrovix were hunted to the edge of extinction (AUDIO: Nevernor) by the Time Lords, (AUDIO: Assets of War) but not completely. Some survived in the Time Vortex.
Thousands of years after their supposed extinction, disruption from the Last Great Time War spilled into the Time Vortex and threatened the Orrovix. (AUDIO: Nevernor)
After Leela was thrown into the heart of the Last Great Time War by the War Master, (AUDIO: The Devil You Know, Mother Tongue) she came to Njagilheim shortly after a battle of the Time War was fought there. The battle left temporal storms swirling backwards through the planet's timeline, making time delicate enough that Leela accidentally caused a paradoxical time loop involving Agata and Ivar. The Orrovix were tracking Leela due to the temporal energy on her from having spent so much time in the Time Vortex while travelling with the Doctor, and this break in time gave them a chance to escape the Vortex to Njagilheim. Leela escaped and left Njagilheim (AUDIO: Nevernor) to eventually arrive at Unity. (AUDIO: Unity)
The time loop continued in Leela's absence and the Orrovix continued to search for a break in time through it. If they were to escape, they could roam the entire timeline of Njagilheim, free from anyone to hunt to them. Romana II and Narvin came to the planet searching for Leela and got caught in the loop. The Orrovix began tracking Romana because she too had spent considerable time in the Vortex, as well as E-Space. Romana and Narvin broke the loop and escaped back to their TARDIS, leaving the Orrovix trapped in the Vortex. (AUDIO: Nevernor)
The Time Lords eventually sought to weaponise the Orrovix. A Time Lord hating Gallifreyan, Rennis, sought to turn the creatures against the Time Lords only for Susan Foreman to tame the creatures, allowing the Time Lords to arrest Rennis. Despite this, Susan began to petition for the Orrovix to be freed. (AUDIO: Assets of War)