Sense Mana

Information 
Tells the caster the mana level at the point where he is standing, and whether the local mana is aspected (see GURPS Fantasy) or otherwise unusual. If the spell is successful, a second casting will reveal the precise nature and level of any aspect or other peculiarity.

Cost: 3. 
Time to cast: 5 seconds. 
Prerequisite: Detect Magic.

Item

• (a) Staff, wand, or jewelry. Usable only by mages.  
  Energy cost to create: 200.
• (b) Ring or necklace. Always on. It vibrates whenever the wearer passes over a boundary between areas of different mana.  
  Energy cost to create: 500.