What Sareth said was what Roy wanted to say.
Due to the millions of years of hostility between flame demons and frost demons, Roy did not want to explain anything to Berial at all. As long as he beat this guy to the ground, everything would be fine.
Roy stretched out his hand to summon Frostmourne, pointed the tip at Berial, and raised his chin. "Come. Although the head of a demon lord is a great battle achievement, you're still useful to me, so I promise I won't kill you for the time being!"
"Arrogant bastard!" Berial roared, and his two front hooves suddenly raised high and stomped on the ground.