The Storm King wanted to rule all of Equestria by himself and didnt need backup or help, Grogar tried to tell him that he could take either Sombra or Mane-Iac with him for help and backup as he's trying to defat the Mane Six but he refuses and claims he can defeat them by himself as he mentions that his traitor Tempest betrayed him and makes it clear that he doesn't want help again.

Prequal to this
www.deviantart.com/kayman13/ar…

Credits

Storm King and Grogar vector by :iconandoanimalia:

Background and Characters by Hasbro. :D (Big Grin)