To tame you need to allow a Reaper Queen to pick you up and impregnate you. Once it has had its way with you, an icon will appear in the bottom right of your screen with a timer and a small exp bar. You need to kill enemies (or maybe craft items, I haven't tested yet) to gain exp and level the dino inside of you. From what I have seen so far they all start at level 1, so when the exp bar says, for example, +44 it means that it will tame out at level 45. When the timer runs out it will burst from your chest Alien style. It will then try and run so make sure you are in a room or enclosed area. You also need to kill Reaper Queens and Kings to get pheromone glands. These need to be eaten to trick the baby into thinking you're a Reaper. You can then claim the baby and it eats raw meat. All I can say is, good luck...

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