Mana is the energy that powers spells.
Worlds in GURPS have different mana levels. Magic does not work on worlds with no mana.
|Very High Mana||Anyone who knows spells can cast them. Very high mana worlds make magic common and more potent, affecting some rules. First, a mage who spends FP (Fatigue Points) to cast a spell on his turn gets those FP back at the start of his next turn. Second, all failures are treated as critical failures – and actual critical failures produce spectacular disasters!|
|High Mana||Anyone who knows spells can cast them.|
|Normal Mana||Only mages can cast spells. This is the default mana level in most fantasy settings: mages use magic, others don’t.|
|Low Mana||Only mages can cast spells. Low mana worlds make magic rare and less potent, affecting some rules. First, all spells perform at -5 to skill, for all purposes. Magic items are similarly affected; see Power of a Magic Item, 4th Edition Basic Set, p. 481. Second, critical failures have mild effects or no effect at all.|
|No Mana||No one can use magic at all. Magic items do not function (but regain their powers when taken to an area with mana). This mana level occurs in isolated spots in magical worlds, but entire worlds can lack mana, making magic use impossible.|