The branch of Naughtymancy ruled by the aspect of Fate Croakamancy has the (somewhat) distasteful function of restoring a semblance of life to the recently croaked, transforming them into the rotten, shambling horrors that are the uncroaked.
Croakamancy has significant limits - the uncroaked have a limited persistance ('lifespan' seems inappropriate somehow) before they rot down and disintergrate and the transition to their new twilight existence robs them of a lot of their higher brain functions: casters lose their magical abilities, warlords lose a great deal of their initiative and command skill and regular units lose pretty much all trace of their identity. However, some abilities are maintained, and an uncroaked warlord can still lead to some degree and uncroaked flying units can still fly.
So far the only known fusion involving Croakamancy was the uncroaking of the Gobwin Knob volcano which ended the Battle of Gobwin Knob. This required the linkup of a Master Dirtamancer (Sizemore Rockwell) and a Master Croakamancer (Wanda Firebaugh) by an experienced Thinkamancer (Maggie). Such an casting should not be expected to occur with any great frequency.