Demon Lord's Reincarnation

I sat on my throne bored, extremely bored. There was nothing else to do, I have done it all. I the Demon Lord Kretos, have done what all the other Demon Lords before me failed to do, I have united the demon race, I also defeated the almost never-ending flow of human heroes. I was even able to conquer the whole continent and with that, there was nothing more. I who adored battle was unbeatable, not even my sons and daughters that I have made with my numerous concubines could match me.

There was no more battle to be had. I sighed once more as I drank the wine my firstborn son gave me. It was a gift for my thousand-year reign. The moment I drank the wine, my body felt groggy, what is this? I'm getting drunk after one drink? The moment I thought of this, someone entered the throne room. The one who entered was a handsome young man, who looked to be in his early twenties, this was my son and with him, he brought a bunch of magicians. He was smirking at me, this crazy son of mine what has he done?

"Good afternoon father, it seems like you're not feeling well."

"Galdo what have you done?"

"Nothing much father I just gave you a mana suppressing drug."

When I heard what my son said, I couldn't help but smile.

"Hahahaha, so it's finally happening my defeat is about to come. It seems like these old bones of mine have forgotten the tension of battle that's why I let my guard down."

"That is indeed true father, so why don't you rest now and hand me the throne."

The moment he finished speaking I dashed forward, ready to strike. Even with my mana suppressed my physical abilities were still excellent. With a sword at hand, I slashed down, at my own son using my full strength, to which he responded by blocking my attack with his own blade.

"Do you think it would be that easy? Do you think I would simply hand you the throne? How about a little bit of excitement before I give it?"

"I would love to play with your father, but... I'm in a hurry to solidify my rule."

The magicians that came with my son started attacking me with a barrage of spells. Without being able to circulate mana into my body I had zero resistance to magic. Still, I kept on fighting, as I smiled while laughing heartily.

I slashed down at my son, who blocked with his own sword. The floor cracked while the hand of my son trembled a bit. 

"As expected of the strongest even without mana your strength is unparalleled." I kept on attacking my son after he said that. Yet even with all my effort without any mana, muscle strength alone cannot bypass someone as strong as my son. 

Not only that this battle was happening while I was being bombarded by spells, that I could not dodge or defend myself. Yet that didn't matter to me, as long as I have my sword at hand, as long as I still have the strength, I will fight. 

After a few minutes of attacking I couldn't move anymore, my body which has survived numerous battles against many powerful foes was now unable to move. I know I'm supposed to feel frustrated after losing, but only feel liberated... So this is what it feels like to be defeated...

"As expected of you father, even without mana you could last this long. No wonder you are considered the strongest demon lord... I know you can't hear me anymore but seeing that stupid smile on your face I knew I did the right thing as your son."

The strongest Demon Lord conqueror of the world died at the hands of his eldest son, and even in the face of defeat he died standing with a big grin on his face.