To tame a reaper king/queen, you need to attack a reaper queen(reaper kings will not work) until she’s is low hp. After that, she will sting you with her tail that will make you pregnant. After you wait a good amount of time, the baby will burst out of your chest. The only way to claim de baby, you need to eat reaper pheromones glands that drops from reapers. Good luck survivors!
Pretty good for fishing or collecting Nameless Poison. For fishing, stand in water where is a lot of fish, and use its AOE attack. Use it again to collect all the fish you killed. For Nameless Poison you need to have a Health/damage oriented Reaper. Find a Nameless, wait for his friends to come and use AOE attack. There is no need to do it again unless you want to collect meat and hide from Namelesses.
Be careful with their jump, its super fun but can quickly land you int the bottom of tge rock drake caverns. If you aren't familiar with the area its very difficult to get out of especially with the radiation.