Overlord_Venus
It seems that author is another victim of myth of how hard it is to attain immortality. This is old learned behavior from our global culture. Like chejc this out, there is skill capable of regenerating almost whole body, unranked skill regen. And if limbs and internal organs can be regenerated then rejuvenation of the existing organs should be simpler therefore. Therefore concept of biological immortality for high lvl elites should be easier than regenerating whole limbs or internal organs. Hell, if there is lifespan just cut the old limbs and regenerate them anew to young age. Also Mc is literally immortal even without consideration I mentioned above. He can simply switch bodies.