Ghost Merging

Ghosts have a peculiar mechanism, called fusion (or more often merging), which allows them to obtain various results (including, very commonly, reproduction).

The fusion of two ghosts consists in the overlapping and partial or total sharing of the ectoplasm of which their bodies are composed. The main types of merging are:

Total merging (or total fusion):

the two ghosts become one body, overlapping one another and letting the other's ectoplasm filter through the natural voids of their own. The result of a total merging is a new ghosts, which possesses the memories of both individuals who were, as well as the powers of both. Usually, with total merging the new individual obtains new abilities and is stronger than his "parents" would have been: the whole is greater than the sum of the parts.

The total merging, after a time ranging from twelve to forty-eight hours, becomes impossible to dissolve and the two ghosts will remain fused for the rest of their lives. The individual resulting from a total merger can independently produce offspring in the first two years from the moment of the fusion, breaking off pieces of its own ectoplasm known as "ghost eggs", which will later develop into small copies of one of the two "parents".

Temporary merging:

the two ghosts become one body, exactly like in total merging, but the fusion of the two bodies, at a microscopic level, is less stable. The result of a temporary merging is a new ghosts, which however can de-merge and return to being the two previous individuals. Usually, with temporary merging the new individual does not gain powers that were not already part of his parents' baggage, furthermore the fusion is unstable and can be de-fused in combat if he receives too much damage.

In short, temporary merging produces a weaker individual than total merging, but has the advantage of being able to be defused, so that the ghost parents return in their original forms. This mode of fusion never results in the production of offspring.

Partial merging or reproductive merging: 

the two ghosts overlap and fuse only a part of their bodies (but always leaving their heads outside the fusion area) for a variable period of time, and then release a part of their ectoplasm, which remains fused with that of the partner. The result of partial merging is a new individual, completely separated from its parents, with its own personality and a small body, in short a ghosts "baby" (called a paralarva). Some species of ghosts are capable of producing multiple new individuals at a time, from two to twelve, with each partial merging.