Compass Spell

Compass spell is a magic spell that creates a virtual temporary compass that points to the closest undiscovered secret room.

Mana Cost
Compass spell is the only spell that costs the same amount of mana all over the world.

Task
This spell is mentioned at the task "Find a hidden room", but it is not actually required to accomplish the task. The requirements are:
 * Have the tech Master Alchemy unlocked
 * Find (with a dwarf or the Magic Light) a hidden room (containing a guardian or not).