The Province of Amalur
Our heroes do not know much about these Slaadi creatures. However they have seen how the Red Slaadi reproduces. It seems to use it’s long claws to inject a small egg into the victim. The egg then gestates and eventually becomes either a blue or green tadpole creature which eats it’s way out of the hosts chest.
The strange drow prisoner within the prison also hinted that the Slaadi were the ones who are capturing people. Trapping them within a place called Limbo for unknown reasons. Taking them from different realms.