Zub is a game written for the Amstrad CPC, Commodore 64 and ZX Spectrum which was published in 1986 by Mastertronic and was written by John and Ste Pickford on the ZX Spectrum and Phillip Brian Allsopp on the Commodore 64 with music on all formats composed by David Whittaker.
Zub is in the employ of Emperor Zub of the Zub galactic empire who has been tasked with retrieving the Green Eye of Zub. In order to facilitate this task, Zub has been permitted use of the ancient intergalactic elevator system which permits transport between planets. The elevators do not follow any sort of linear route and must be reached by traversing and riding platforms on planets to reach any of the three elevators at the top of the chain.
The platforms and elevators are guarded by creatures confusingly known as Zubs but each planet has a different sub-species - for example the first level's Zub resembles a gyroscope whilst he fourth level's is a fish. The Zubs can be shot and stunned. They will float to the top platform level and then descend to harass and attack Zub. The Green Eye of Zub was last located on the tenth planet and once the Eye is found, Zub has to return to the first planet to present the Eye of Zub to Emperor Zub.
Source: Wikipedia, "Zub", available under the CC-BY-SA License.