Arrowheads are pointy pieces of Psitanium, and can be found in places that emit purple fumes.
Deep Arrowheads Edit
These larger, more valuable arrowheads are buried deeper underground, so they can only be found with a Dowsing Rod, available at the Main Lodge. These are worth much more than the normal arrowheads.
Mental Arrowheads Edit
These are echoes of Psitanium energy found in the mental world. Mental arrowheads add to Raz's total Psitanium value.
After completing Basic Braining, trying to leave the Kids' Cabins area makes Kitty and Franke ask for a payment of one arrowhead to continue. Later in the game, arrowheads are needed to buy the Mental Cobweb Duster in order to progress through the Milkman Conspiracy. Later on, however, arrowheads are no longer of any importance to the story, save for purchasing items, of course.