Read manga: Birth Of Evil

Manhwa
Summary:

Agne is an evil wizard who wishes for the end of the world. In order to achieve his goal, he summons a Demon King - and as he materialised from the abyss, he would proceed to end the world as Agne wished... or not. Summoned with an imperfect memory, the Demon King decides not to end the world as Agne had wished, but rather the opposite...