Sandstorm is an angry, whirling, personification of a sand storm who lives in the Desert of Nightmares on the planet Xooberon. As part of Vince's test of being 'The Chosen One', the blue inhabitants of the Desert force him to confront the sand monster.
Sandstorm is completely made of sandpaper - even his palms are sanding discs which causes him to erode everything he touches - which in turn causes him to be permanently angry and frustrated. When Vince discovers the cause of his rage he advises him to 'accessorise', and gives him a pair of gloves. With these gloves Sand is delightedly able to enjoy 'self love' (masturbation), and thus owes Vince a debt of gratitude.
He later repays the debt by sanding down Evil Tree and saving Vince and Howard.
In many ways Sandstorm is similar to Mr Susan, the same mannerisms, the same tight voice, and is also shrouded from head to toe in material, but in this case sandpaper.