@@Magnifier or Congero Potentia was a taboo in God realm because it was the only reason the Supreme god won the war against King Caligo the biggest ruler ever in Asura clan, this happened before mortal realm was made and many people believe it a myth.
War Of Great Purge
That was the time when there were no mortals in entire universe and only gods existed and Supreme God was there ruler, ruling along with him was holy goddess. Everything was going well when suddenly Asura's declared war against Supreme God it was said Caligo loved holy goddess and when his affection was not received he revolted.
Some say Caligo was brother of Supreme god and he was equally powerful at that time and his army was equally powerful even more so as compared to Supreme God. Finally the war started and their was heavy losses on both side and no one accepted defeat, but Prince Leith son of Supreme God and holy goddess collaborated with Caligo as he was tired living in their shadow and wanted their power poisoned Supreme God, because of poisoning he could only use his power once and make and impact or the war was lost and that's when Holy goddess supported them from behind and released her power of Congero Potentia.
The last attack that Supreme god sent on Caligo killed him on spot and Leith disappeared forever, which was a mystery forever. Due to being poisoned and holy goddess used her power to extreme potential after the attack both of them turned to light and disappeared forever and after that no one had the ability of Congero Potentia, which can increase potential of ones power to infinite degree. This was a big blessing and biggest curse of Overlord because his heart was experiencing fear that he had never felt before.