Like, how am I allowed to use this? Can I use it commercially, do I have to give credit etc
It was mostly just created to add an extra monster to fight, but most definitely!
You would have to give credit to me as well as Delphi who collaborated with me on creating it, but it's created under the the third party Mörk Borg and Vast Grimm licenses, so you could definitely use the character and it's likeness. You'd have to find or create art for it though, as well as put the necessary labels. All the information is here: https://vastgrimm.com/the-horde/