Unicron Singularity

The Unicron Singularity is a frightening space-time anomaly, resembling a black hole, near Cybertron.

"This thing you speak of, it is no ordinary black hole."

- Primus, "Balance"

Cybertron cartoon
The giant black hole was created by the destruction of Unicron. Threatening to consume Cybertron, it forced the planet's inhabitants to evacuate. Red Alert's attempts to seal the black hole with an energy grid failed.

Vector Prime informed the Autobots that 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. This revelation set off a long-running quest to retrieve these scattered artifacts.

Fun Publications comics
Vector Prime revealed that the singularity was created when Primus's plan to trap Unicron in an Energon Sun, giving off life rather than consuming it, spectacularly backfired. The sun instead collapsed into a black hole which consumed the infant universe it had once nurtured, and then expanded into space near Cybertron.

The black hole's pull was so strong that even Unicron's presence in alternate realities were drawn into it, throwing the entire universal balance out of whack. As the Unicron Singularity replicated itself across these worlds, its space-time distortions drew them together, histories overlapping in a somewhat messy faction.

The continued expansion of the Unicron Singularity threatened to consume the entire Universe and, owing to its self-replicating nature, eventually the entire multiverse.

The "Cybertron" universe
It is unclear whether the Unicron Trilogy caused a "Crisis" event—permanently merging the universes caught in its snare into one, somehow jumbling them all while remaining separate, or possibly drawing them together at the point of the Singularity and releasing them after. What is clear is that the temporal changes seem to be permanent, and show no signs of 'unraveling' after the Singularity's destruction—individuals, events and locations from multiple universes now permanently co-existing in one. (The first scenario, for all intents and purposes.)

Universes involved
While the "gestalt" reality created by the Unicron Trilogy draws heavily on the Dreamwave Armada and Energon comics (Over-Run's backstory); and the Armada and Energon cartoons (the creation of the [[Energon Orb|Energon Sun]), there is some indication that other realities are also involved. The capital of Cybertron in the new reality is suddenly Iacon (Generation One) rather than Cyber City (comic) or Central City (cartoon).

The Four wise elders would also seem to indicate a Generation One connection - but their presence in the Unicron Trilogy universe seems to predate the Unicron Singularity, and is more likely mundane time-travel. That kind of thing happens a lot in Transformers.

All this adds up to an all-purpose answer for glaring continuity errors ''EVEN ONES NOT IN THE TRANSFORMERS UNIVERSES. That's right, it sucks up continuity along with everything else.''