The Beast Rain Project was something that the New Elian Kingdom created in order to have stronger soldiers.
The purpose this project was to create sub-humanoid warriors infusing them with animal genes.
The ideal warrior that was a product of this project was Bearman who still retained his human form but had the strength of a bear, powered up by his suit.
Those that were more of a proto-type Beast Rain Project subject were people like Ian and Jack, who retained a more animal like appearance.
Eventually Klein was recruited after graduating the Ketarh Magic Academy, he was asked to teleport the warriors all over the Arc continent in order to make it easier for them. But unbeknownst to him he was teleporting them behind enemy lines.
Soon Klein and Sione's husband Cain found out the truth that about the Beast Rain Project and destroyed the lab.