LEGENDARY SPECIES: THE HAND / THIRDSPACE ALIENS

The Hand are an ancient and powerful race said to have been imprisoned in another dimension over a million years ago by another powerful race.

The species refered to as the Thirdspace aliens was encountered by the Vorlons species a a million years ago, when they decided to build a gate to open a doorway to what they believed was the Well of Souls, the source of life. What they reaches was the Thirdspace aliens' dimension. During the ensuing battle, ehe aliens took telepathic control of many Vorlons and forced them to fight each other. They were finally forced to their own dimension. A group of Vorlons, still under the control of the Thirdspace aliens, captured the artifact and jettisoned it into hyperspace, hoping to recover it later.
Shrowded in mystery nad lgends, the Hand and the Thirdspace aliens may or may not be the same. Both legends talk about a very powerful and evil species that was locked in another dimension circa a million years ago by another one. Their appearance remains a mystery. During an encounter with an invading Thirdspace armada, a large, octopoid-like creatures was seen but it may also have been one of the degenerated vorlon under thirdspace control as this other secretive species, for what has been glimpsed of it might be vaguely octopoid.
Source: Babylon 5 universe.