destroying the orb requires a wizard in your party

Brune doesn't sell a scroll of gust of wind, a required component of destroying the skull...

As such you have to either cheat with the console, or you have to have a wizard in the party research the spell on level up and then scribe it to a scroll.

 

You don't. A scroll of Gust of Wind is among the loot you find throughout the game. Unless I'm wrong, same chest as the Skull. In fact, I've destroyed the Skull with a wizard-less party before.

 

I think there is a scroll of gust of wind in the chest on level 3 where you kill that hag creature. I think the radiant spiked chain is there too.

 

aha. I missed that part.
I think I know how. My last playthrough I talked about destroying the orb before I found this. I managed to get the spell on levelup and scribe it... so that when I finally found it i just ended up selling it (identify, can I scribe it? no... sell) without even noticing what it was a scroll of. (I sell any scroll I can't scribe by my wizard)

 

Find the Banshee and you find the scroll.