The Hand in the Sand/Quick guide

A helping hand

 * Talk to Bert near Yanille's house portal. (Chat options 2-2)
 * Give the Guard Captain in the nearby pub a beer.
 * Ring the bell outside the Wizards Guild to the east.
 * Return to Bert.
 * Make your way to Brimhaven, find Sandy in the small house just south of the Shrimp and Parrot.
 * Search his desk.
 * Pickpocket Sandy until you get some sand (may take multiple attempts).
 * Talk to Bert.
 * Ring the bell and talk to Zavistic Rarve again.

Truth serum

 * Make your way to Port Sarim and find Betty in her Magic Shop. (Optional: talk to Rarve again and ask for more help, and he will teleport you straight to Betty in exchange for 1 vial)
 * Talk to Betty.
 * Use your Redberries then your Whiteberries on the vial Betty gave you, and use the dye on your Lantern Lens.
 * Talk to Betty again.
 * Open the door to her shop and stand in the doorway, then use your Lens on the counter.
 * Talk to Betty again.
 * Make your way back to Brimhaven.
 * Talk to Sandy, choose any option to distract him.
 * Use the Truth Serum on the coffee mug on the table.
 * Activate the Magic Orb in your inventory.
 * Confront Sandy until he confesses.

Retrieving the head

 * Head back to the Wizards Guild and ring the bell once more.
 * Talk to Zavistic Rarve twice and a cutscene will start.
 * Make your way to the sand pit on Entrana and talk to Mazion.
 * Talk to Zavistic Rarve.
 * Quest complete!