The Unicron Singularity is a frightening black hole near Cybertron that threatens to swallow it, and eventually the rest of the universe, whole. The only way to destroy it and put the universe back in order is to gather up the four Cyber Planet Keys and the Omega Lock, hidden on various planets, and use them to awaken Primus.
The Unicron Singularity was born after the end of the Powerlinx Battles as a result of Primus' attempt to bury his eternal nemesis Unicron in the center of a newborn sun. This plan backfired, and Unicron's essence collapsed in on itself, creating a black hole. The black hole's pull was so strong even Unicron's presence in alternate realities was affected, and the fabric of space-time itself was increasingly unstable, altering even the minds, memories, and histories of all who live within this chaotic universe.
All this adds up to an all purpose answer for glaring continuity errors. That's right - it sucks up continuity along with everything else.
- The Fun Publications Cybertron fan club comic created the idea that the Unicron Singularity was warping and altering space-time to explain away continuity errors between the English dub of the Cybertron cartoon and the two previous series that it was supposed to be a sequel to. It is possible that it could also be used as a blanket explanation for continuity errors in the previous series and things like Sky Shadow's backstory as well. Using this excuse, one could effectively explain away every plot hole from every fictional continuity ever, even non-Transformers series. Gotta love FP.
- The alternate, stand-alone Japanese version of Cybertron, Galaxy Force, made no blatant stated connection between Unicron and the "Grand Black Hole." However, the Grand Black Hole appeared in the present time because the (unspecified) Dark God, the source of darkness in the universe that opposes Primus, was trapped within a Matrix-type object, separating it from the universal balance. Although, since then, Takara has released an official timeline of events that ties up the three series. The explanation given for the Grand Black Hole now agrees with the American fiction.
- The planet Cybertron itself was swallowed up by the Grand Black Hole in Galaxy Force's first episode. In the American version, these scenes were omitted, and the black hole merely hovered threateningly near the planet. This does make more sense, given that characters would return to the planet later in the series and not face any of the negative effects of being in a black hole, such as dying horribly.