If you put foundations under the reaper it can not burry. This way you can keep farming the same reaper for the best stats because every baby reaper, even if its from the same queen, will have different stats.
To obtain a reaper king you must first find a reaper queen which you must then lower their health to almost dead after you have done this you will have to tank its hits for a while whilst you wait for it to impregnate you once it does this it will bury back underground leaving you at severely low health, at this point you should return to your base where you should have reaper pheramone glands which are obtained by killing reapers however whilst you wait you can gain experience by killing things which will increase the level of your reaper king after it burst, after the 12 hour long wait from first being impregnated is over you should consume a pheramone gland which will alow you to imprint to the baby after it has burst out of you withought killing you, after you have imprinted on it you just raise it much like any other meat eater feeding it raw meat until it matures however if you would like to aquire multiples of these creature you will have to repeat the process ovee again.
Take a high level rock drake to find these things. Bring the health of the reaper queen to BELOW 2000. Then hit the Queen with a pickaxe while on the drake. She will grab you right off of it and impregnate you. Took me about ten minutes of hitting her on a level 200 drake with high health and and a melee damage rate of about 2000. You can check her health level with a magnifying glass while Your drake recharges it’s stamina.