Not native to the hyperspace dimensions (no life-form is, after all), these creatures are occasionally carried there attached to the hulls of starships. In real space they present little danger, since they get all the nourishment they need and more by surfing the solar wind in the inner circles of a solar system. In hyperspace, that abundant energy source is no longer available, and they gravitate towards the only useable energy sources there -- ships and beacon stations. In small numbers they pose no great threat, though even a small group can drain enough power to noticeably degrade a ship's performance. On rare occasions though, a swarm of hundreds or even thousands can form and then they can consume enough of a ship's power to effectively shut it down. The dangers inherent in this event are obvious; without power the ship (or station) will have no life support, no communications, and no propulsion.
These creatures look like scintillating protoplasmic starfish, or giant tentacled amoeba. As they feed on energy, lights of all colours ripple through their translucent bodies creating a beautiful display.
The Energy Leech's tactics are simplicity itself; it moves directly towards the most abundant nearby power source and drains energy from it. It is capable of self-powered movement in zero-G, using a biological process very similar to that of the reactionless drive commonly used in most space craft. Their rate of acceleration is quite low compared with most spacecraft; they are capable of only 0.15G. Given time however they are capable of quite a respectable velocity (38,400,000 km/h in 75 days, 9 hours, 21 minutes and 12 seconds)
By the very nature of the leech, energy weapons are useless against them -- in fact, they positively enjoy being subjected to the tingling caresses of lasers or plasma weapons. Furthermore, the concentrated energy used in most weapon attacks can force them into a process of reproductive fission; as they absorb energy from the attack they appear to swell, and eventually split into two identical entities. They are, however, almost defenceless against physical attacks.
The leech is blind except for its energy detection sense, and stone deaf. They communicate amongst themselves in a limited fashion by radio waves; they can both send and perceive in the radio spectrum.
Mindless animal motivations. The Energy Leech's only purpose is to find and absorb energy from the nearest and most abundant source.
These creatures are not designed as a threat individually; one guy with a pair of brass knuckles could take them out one-on-one without any trouble whatever. To be a meaningful threat they should appear in a swarm.