Kroton universe

In an alternate universe, the Krotons, organised into the Kroton Imperium, were the dominant power of their reality, theorised by the Fourth Doctor to be the result of a hypothetical absence of the Daleks. A fleet passed into a gate through the Void to N-Space and engaged in battle with alternate Quarks who had arrived the same way. Discovering the Doctor's TARDIS, they engaged a transmat opposing that of the Quarks to bring it aboard, with the Fourth Doctor and Romana II taking the chance and boarding one ship, which they found inhabited by advanced Krotons, to stop the tug of war.

A boarding party of Quarks was transmated to the ship to intercept but was quickly destroyed by the Krotons. Soon after, both Kroton and Quark fleets were attacked by forces of the Ogron Confederation of Planets who, coming from yet another universe, sought to cease hostilities between what they saw as "lesser-evolved species" via the use of deadly force. Ultimately, all three sides retreated to face a crisis in their respective universes. (COMIC: The Lost Dimension)

Other information
Interestingly, when the Second Doctor first encountered stranded Krotons, they wished to return to their "own cosmos." (TV: The Krotons)