Necromancers along with multiple other groups of spell casters were researching a way to make a powerful army in the quickest amount of time. Using the strong orc as a base they experimented with it until they added fungal traits to it to increase reproductive speed. This change allowed the fungal orcs to replicate to fast to be culled and their escape from where they were being researched. This fast reproductive speed has allowed this force to expand continuously eventually absorbing all of the Northeast corner of the world. Wiping out everything they met. They act as a quasi hivemind not sharing thoughts but mentally being able to Shar them. That trait has allowed them to communicate among themselves and has mostly prevented cannibalism but as they run out of food they have begun to feed on each other.