Anti-matter organism

From Tardis Wiki, the free Doctor Who reference

The anti-matter organism was an intelligent blob of energy, capable of existing in both the universes of matter and anti-matter. The organism was used by Omega to hunt down the Doctor and, acting as a bridge, take him to the anti-matter universe.

However, the presence of more than one Time Lord confused the organism, causing it to send more than one individual into Omega's domain. (TV: The Three Doctors)