Zanhoshi Fusion

When Ultimate Swords from different Verses are brought within proximity of one another, whether spatially, temporally, or metaphorically, the twin swords and Verses will begin to merge into one another until only one sword and Verse remain. Throughout this process, various parts of either Verses' continuities will transfer to the other, potentially resulting in a cascade of new interactions that actively shape the retcon process. After a fusion is complete, the remaining singular Verse and Zanhoshi will be new and distinct from their predecessors. Inhabitants of the new Verse who lack extra-dimensional perspective will have no memory of previous continuities, or of the nature of Zanhoshi Fusion.

This process is crucial to the mending of LOTUS's fractured Primeverse. It features prominently in the plot, confusing both readers and characters alike up until the final Zanhoshi Reunion.

Trivia

 * Zanhoshi Fusion was inspired by the woes of one ZTG Dev, who could never decide which alternate version of a story to write down, and kept switching between continuities on the fly by accident. This bug was declared a feature, and realtime retcons became central to the plot.
 * No Zanhoshi Fusion can result in a Verse devoid of Mezzo. It would just be too cruel.