The way you can get your hands on one is horrible.

You have to find reaper queen an get it to REALLY low health like 10% I believe,after that it should try to throw some wird thing on you like in alien movies and that impregnates you.

You should build a box before your baby comes out cause you cant controll it when it jumps out of your stomach(but you can acces it's inventory). You have to consume reaper pheramone garhered from harvesting reapers before it comes out cause it'll kill you if you don't (also I think reaper pheramone is used to imprint reaper king aswell)and feed it with raw meat till it's done.If I made a mistake on something,please correct me so other people can see.

More Reaper Taming & KO Tips