Omniverse

Beyond the Transformers multiverse is the Omniverse, which consists of every possible reality imaginable. Most of them have no Transformers whatsoever while many others are inimical to both human and Transformer life.

Primus wishes to join the Omniversal Matrix when he has completed his cosmic mission, and The Fallen has been classified as an "Omniversal Tyrant".

Fiction

Ask Vector Prime

Vector Prime described the Omniverse as the realm outside of the Transformers multiverse. Occasionally, quantum-string vibrations can cause other realities in the Omniverse to temporarily merge with the universal streams in Vector Prime's domain. Lambda-class universes are apparently most susceptible to this dimensional bleed with the rest of the Omniverse. Likewise, universes in the Lukas cluster have particularly thin barriers, and overlap with other realities in the Omniverse.

The planet Sandra is from a universe outside the dominion of either Vector Prime or the Alternity. Presumably, this would mean that it is from somewhere else in the Omniverse.

Although Vector Prime cannot directly travel to other realities beyond the multiverse, he has a limited ability to comprehend activity elsewhere in the Omniverse. The Prime expressed a particular fondness for the adventures of a hero named "Benjamin Kirby Tennyson", and speculated that his home reality may have interacted with a Malgus-class universe at some point. Vector Prime also speculated that the mysterious Doctor hailed from some other reality in the Omniverse, although he may have travelled through the Transformers multiverse at some point. Ask Vector Prime

TransTech

A week after the Waruder invasion of Cybertron, Minister of Higher Dimensional Sciences Rhinox explained in an interview with Axiom Nexus News reporter Rook that the Waruder invasion had caught the authorities by surprise because their home in the newly-named Cymond universal cluster was previously thought to be outside of the multiverse.

When an Offworlder Zone Security Administration team led by Cheetor arrived at Sideways's hideout in the Heap, they found their way into the building blocked by an Absolute Terror Field, which had somehow been back-doored into Axiom Nexus by an extra-multiversal source by a recent quantum alignment event. Rook - Axiom Nexus News: Investigative Journalist

Notes

• In the real world, the concept of "the Omniverse" originated from analysis of comic-book continuities. As coined by Mark Gruenwald, it meant the collection of all multiverses; for example, Marvel Comics had one multiverse, DC Comics had another, and the Omniverse encompassed both. This extended to all fiction, and in today's usage it is sometimes meant to include the real world as well. Note however, that not every fiction franchise accepts the concept of the omniverse.
• Obviously, the Transformers multiverse would fall under the above umbrella. While there have been crossovers between Transformers and non-Hasbro properties, such as Star Wars and some Marvel superheroes, the term "Omniverse" had never been specifically used around or within them. 2015's Ask Vector Prime feature finally canonized the concept of the Omniverse as existing "outside" the established Transformers multiverse, and encompassing every fictional world ever created that doesn't involve the Transformers.
• In the story treatment that Simon Furman originally presented to IDW Publishing for their comic series, he described a Unicron-driven, simultaneous threat to Generation 1 and Cybertron universes, as well as others unnamed. He called this "an omniverse in chaos".