X-Men and the Micronauts #1 (1983)

First Encounter
The Microverse is under attack by so fearsome a foe that the tyrant Karza and the rebel heroes called the Micronauts have been forced into an alliance against this horrible Entity. The entity proves his might by single-handedly destroying an entire world, decimating Karza’s troops and capturing the Micronauts in the process. Only the Micronauts’ Bioship, with Karza aboard, can flee and follow the Entity’s trail of power to the Macroverse, where it leads them to Professor Charles Xavier. Karza attacks Xavier and the New Mutants and even manages to hold himself against some X-Men. When Kitty Pryde tries shortcircuiting him by phasing through him, instead their minds are displaced, which nobody realizes, as Karza in Kitty’s body still controls his armor. The Bioship explains everything to the X-Men and they decide to help. The Bioship shrinks them and transports them to the Microverse, while Xavier remains behind and tries to find the link to the mysterious Entity.
Release Date: 1983