If you plan on battling reaper king, have a decent mount that can tank and possess an AoE attack/push back attack. Killed one on a Spino in 3 minute. Smaller animal will get killed easily. Difficulty 6 server setting for reference and vanilla stat modifier.
If you happen to find a Reaper Queen in the rad zone, I recommend not going much further or you will find yourself overwhelmed very quickly! It seems once you run over their spawns they spawn more often, so when you’ve fought a few queens and think to yourself “my health is low, I need to leave” there is very likely more queens waiting for you on the way out!
PLANT SPECIES Z IS YOUR FRIEND: heals your mount super fast and provides a charge light just by standing next to it!