Role in the series
Zoster first appears in the issue Ombre su Venere (Shadows On Venus); the Chief Physician has an important mission: allow the Evronian race to exploit negative emotions (generated by hate, resentment, envy...). He needs a guinea pig to test his experiments so, with help of General Zondag's soldiers, kidnaps Angus Fangus, a real concentration of such emotions. His plan falls in pieces, however, due to the intervention of The Duck Avenger, Uno, and Xadhoom. The ship where Zoster is is destroyed by Xadhoom, with the Duck Avenger saving Angus just in time.
However, this isn't the end of Zoster. In PKNA #15 Motore/Azione (Set/Action) we find both Zondag and Zoster are alive and well, after having regressed to spore state to survive in space until they were rescued by the Evronian empire and artificially accelerated back into adulthood (though Zoster keeps his bionic eye). In this story, the Evronians kidnap the cast of the soap opera "Anxieties" (which, according to the Evronians, channels the audience's emotions) in the republic of Providencia, Central America. The plan fails thanks to the Duck Avenger, and Zoster activates the self-destruction of the Evronian base, being seemingly caught by the explosion.
Zoster returns in PKNA #46 Nell'Ombra (In The Shadow), much stronger, more ruthless and determined than ever. Blinded with rage after finding about the destruction of Evron and the end of the Evronian empire, Zoster allies with some alien warriors and tries to get the power of the deceased Xadhoom. He finally succeeds, becoming huge and strong to the point to being capable to erase planets with a mere gesture. However, he is only guided by a desire for glory and superiority over all, he doesn't have control over the power, and it results counter-productive: it can be clearly seen his body recovering his simple Evronian form and then disintegrating in a series of organic fragments. This is the first explicit, unambiguous death of an Evronian, and quite graphic for a Disney publication.
PK: Out of the ShadowsLevel 8 includes a boss fight against Zoster. He attachs from a machine at the center of the stage and the Duck Avenger must shoot the machine weak spot that is exposed for a few seconds.