After getting betrayed by his wife and daughter who married the prince, dungeons appeared out of nowhere and humans were able to use magic like in the fairy tail. Lucas was then summoned by the prince to check out the dungeon in hope to get rid of him there sent him to the last and most powerful dungeon 'the end'.
When Lucas finally got to the dungeons he was greeted by hordes of monsters as he was fighting the horde of monster he was stabbed at the back by his own daughter and left to die not only did she and the mother betray him they plot to kill him he swore when he gets out he will have revenge, the final boss took interest in him and also pitied him and asked if he went to be saved and get revenge on does who wronged him, he agreed on the condition he becomes the successor of the final boss and he agreed. so he started training him in all forms of martial arts and weapons and he mastered it all in 10 years which is about 6 month in the real world and it took him 20yrs to learn all the different types of magic which are: fire, water, wind, earth, light, darkness, space and time.
During the training he meet the dungeon's boss daughter's named:Alice, Maria, Lisa and yumi. When he was done with his training 3yrs has passed in the real world and it was finally time for him to leave the dungeon. azathoth (the name of the final boss) told Lucas his name and told him to look after his daughter's as he left the dungeon with them