To tame a Reaper in Ark: Survival Evolved, you must first locate and provoke a Reaper Queen in the depths of the Aberration's radioactive areas. Ensure you're at full health, as you'll need to allow the Queen to drop your health below 10% for her to initiate her impregnation attack. Once impregnated, escape and avoid death until the gestation process completes. Upon birth, the baby Reaper will emerge, and you'll need to claim it quickly. Remember, the baby Reaper will only eat Nameless Venom, so have a good supply on hand to feed and nurture it to adulthood.

Passive: You need to tame it while the Reaper King is awake.