Fog of Concealing

The village of Katzu has remained safe over the centuries because of the mages of the village.  They have developed a spell which allows them to conceal the village with a deep fog that seems to roll in from no where.  Because they are near a lake, (though not right on it), the fog rolling into the area doesn't look very suspicious, (a perception check of very hard would make some one wonder what was going on).

The spell requires at least four mages, one at each direction point around the village, but more makes the spell more powerful.  The fog will roll in to cover the village very quickly, but for those coming toward the village it appears to roll in slowly and make visibility very hard.  (An appropriate spell resistance can be used to disbelieve.)  The mages of the village make sure they have strong apprentices to learn this spell because it is so important to the safety of the village.  And if an adventuring group has proved time and again they want to help the village, the mages are likely to give the spell to a mage of the adventuring party.

How Spells Work

Mage and priest spells work pretty much the same as each other. Each will call upon either the elements or their Gods in the language of the arcane (Latin if you are equating it to something on Earth), gathering the magic around them to focus the power. This does take something from the mages or priests, which is why it takes time for mages and priests to cast more and more spells, as well as more powerful spells, each day before they have to rest.

Those who cast spells spontaneously (with out study) draw the power form within. Clan Warriors, Spellswords, and bards all use single word, or just a few word, spells of power which draw a lot of energy from themselves. They can cast spells the more traditional way, but don't normally need to study. (Though if they do they can cast like mages.)