User blog comment:IamJakuhoRaikoben/Chapter 332: Fire Bird, Review./@comment-4933386-20130525123925/@comment-7418318-20130527230923

What about the following scenario?

Sting finds out that the "evil mastermind" is f-Rogue and reasons that if he kills present Rogue, the damage will come undone.

Rogue defends himself and (after eating his White Dragon Slayer Magic) ends up killing Sting. Deeply disturbed he retreates to some hideout. Due to living in seclusion he happens to get through Acnalogia's rampages unscathed.

While he hides away from the world, his guilty concious builds up the phantasy that he killed Sting intentionally to steal his power. And from there his maddened mind starts to seek world-domination through the power of Dragons.