To tame this you should let a reaper queen impreg you, to do that you have to almost kill her, she has to have around 250 health then when you are β€œpregnated” a timer will appear when it comes to 0 reaper king will be born and you should be in a safety box when that happens because he will ran away and very very fast and you cant control it. Try to feed it with tons of meat and when he grew up a little you can get it out of the box

Note: the box should be small it is better so he can move a lot

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