I charged their characters about 300-500 gp to work with the local ceramics shop and do the research for supplies, and a cost for the arrows I forget. Probably about 5 gp each. Their characters got the HW from the local Church.

Some Links

• Character create
• single class hit points
• hit points, multi-class

My players invented a small ceramic cover for Continual Light arrows. They need to light up an area beyond bullseye lantern range, they fire off an arrow, the ceramic breaks, and the distant area is now lit up with Continual Light. Their characters did their own casting of CL.

Of course, the corridors/rooms have to be high enough to get any distance.