I don't know whether to sell it or keep it lol.

I say sell it..but then I love to hoard sp LOL

Lol, thanks the advice. I'll decide later what to do with it.

I'd say sell ir or put it in your wardrobe if you want the achievement later. You can also turn it in to the mage.

It is according on whether you would rather try for an achievement or get the sp. You could give it to the mage and hope to get a tome which is an achievement. Also there is an achievement for having all the mages in your wardrobe.