Genesis 2 is the easiest map to get a reaper. Go to Rockwell's innards near the boss fight terminal and lure a reaper queen below it. The pit that it falls into will fill with acid that damages it. Once it gets to 2k health, lure it out for it to impregnate you (you may want a trap because it will still try to attack you). While pregnant, gaining exp will level up the reaper, it max out at 75+ levels. If you are struggling, then I suggest watching Raasclark on youtube. Good luck.

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