Currently nemeses are unloaded when the chunk they are in unloads. To fix issues with that approach, instead mark the nemesis as chunkUnloaded when the chunk unloads. The reaper will periodically scan through all loaded nemeses and unload the ones it can. There should be a fixed time the nemeses must remain chunkUnloaded before being picked up by the reaper. There should also be some logic to cleanup nemesis that are marked as loaded, but the entity ID cannot be found.