Legion

The Legions were a race of beings who posed a threat because of their misuse of temporal powers. They existed in seven dimensions.

Biology
Because of their multi-dimensional aspect, Legions appeared to humans as a group of disconnected shapes moving in and out of the usual three: a three-dimensional cross-section of a seven-dimensional object. Because of this, their voices changed pitch erratically. They could also drift around in Time if they weren't concentrating. If they reappeared in the main three dimensions within another being, they ripped that being apart. (NA: Lucifer Rising)

Technology
The Crystal Bucephalus restaurant used technology similar to that of a TARDIS, which was directed by a Legion Tank. (MA: The Crystal Bucephalus) IMC's quantum collapsers were also harnessed from the Legions. (MA: Lucifer Rising)

History
Species that the Legions had encountered include the Cimliss, the Usurians, and the Okk. (MA: Lucifer Rising)

In 2157, the Legion aided IMC in taking over Lucifer. (NA: Lucifer Rising)


 * "Lucifer Rising" refers to "Legion" as an individual whereas "The Crystal Bucephalus" states Legion is a species. This might be explained if the Legions were a hive mind, implying there were all one being.

In the 2700s, the Time Lords punished the Legions who used their temporal gifts to undermine the business consortia that ruled the galaxy. The CIA errected temporal inhibitors on their world and the Time Lords developed a standard sentence of one hundred fifty thousand years imprisonment for races that misued their temporal powers on the scale that the Legions did. They were eventually freed. (MA: The Crystal Bucephalus)

At some point, a Legion joined the Sixth Doctor and Grant Markham on their travels in the TARDIS. Before it left under unknown circumstances, before Grant himself left. (CP: Perfect Timing: Schrödinger's Botanist)