Onihr

The Onihr were a species who sought to become the lords of time after the War.

Biology
The Onihr were rhinoceros-like humanoids, with short legs, long arms and horns. They had poor eyesight but a highly developed sense of smell. Barring accidents, the Onihr were immortal. (PROSE: Trading Futures)

Culture
The Onihr valued the heroic loss of one life for many. (PROSE: Trading Futures)

Technology
Onihr ships were designed with aesthetics in mind. They travelled by teleportation, but only at light speed. They were unable to master time travel, and therefore wanted the Eighth Doctor to build a time machine for them. They considered themselves to have advanced technology, but Fitz noted that their holographic recreations were of poor quality, and their pain stimulator just made him remember past experiences where he had been in pain rather than actually making him experience fresh pain, which actually made him feel better by distracting him from his current injuries. (PROSE: Trading Futures)

History
The Onihr sought to become the lords of time, and searched for the secrets of time travel for millennia. They found fragments of time travel knowledge and technology scattered on planets throughout the galaxy, including the high-collared robes worn by the Time Lords. They attempted to acquire the Doctor to learn the secrets of time travel, but accidentally captured Fitz Kreiner by mistake (They could identify time travellers by the energy they picked up through time travel, and, knowing that the Doctor currently had one heart, assumed that Fitz was the Doctor). After failing to bluff them into backing off, Fitz subsequently destroyed the Onihr fleet by setting their ultimate weapon- a massive gun that generated a powerful EMP- to backfire, destroying the fleet preparing to invade Earth. While a few Onihr survived this as they had been off their ship at the time of the attack, they soon recognised and accepted that there was no benefit in continuing to attempt further invasion, and decided to accept their loss and teleport home at lightspeed. (PROSE: Trading Futures)

Behind the scenes

 * Onihr is "rhino" spelled backward.
 * The Onihr are notably similar in description to the Judoon, who would be introduced six years later in TV: Smith and Jones.