Past and Future

Argos Belmont, the Revenant Sovereign and also the King of Belmont Kingdom revealed the past of the entity he was conversing with through the Mirror of Fate. 

The 7th stage saint individual he was talking with had a terrifying past as he was once a member of the 8th Hero of Darkness' party. This type of background was enough to get anyone killed even to this day although these events took place 300 years ago. 

"You dare, Argos! You think I'm afraid?!" he bellowed in rage while expressing visible hatred. 

And the target of this hatred wasn't the vampire king but the deceased 8th Hero of Darkness himself. 

"I trained with him, I fought by his side in many battles. 

I trusted him like my brother!" he spoke in a furious voice. 

"I believed in him blindly without ever questioning his judgment. 

And what did he do? 

He went on a suicide mission and caused mayhem in the entire world by killing the other Heroes.