For Valhalla is when you are having sexual intercourse with a girl (or a guy) and you want to step up your kinky side and grab a knife and stab your self in the chest while screaming out for Valhalla whilst viscously fucking them until you either cum of bleed out and if you cum you may survive if not you will be remembered in Valhalla and the great sexual king.
"baby I want to step this up I think I'm gonna perform For-Valhalla tonight to show my love for you and my manliness