Mists

There are two different definitions in the old world of darkness system for the mists:

Mists, capital M

This refers to the Mists that were present before the creation of anything, the grand pool of creativity that no longer exists. This is the primordial goo the Tuatha de Danaan sprang from.

mists, lower case m

This refers to the phenomenon that Changelings experience on entering and leaving different levels of the Dreaming.

mists and Changelings in the Dreaming

A changeling in the real world can only remember a certain amount of her Mein. When entering the dreaming, and on going deeper into the dreaming, more and more of the fae self is restored and remembered, due to the "lightening of the mists". It's analogous to a deep fog keeping certain secrets from the world, and lifting when there's no banality around to affect the memories being hidden.

mists and Changelings out of the Dreaming

A changeling who has forgotten her fae mien is said to have "succumbed to the mists." This problem is typically reversed by having another changeling enchant the changeling who forgot herself.

mists and the Effects on Mortals and Cantrips

Changelings casting cantrips or enchanting people will find that mortal humans will slowly but surely forget everything that occured about a cantrip cast in front of them. It's a self-defense mode for the Dreaming -- keeping mortals from remembering the chimerical wonders of the world, and safely hiding the fae.

An enchanted person, once the enchantment wears off, will quickly forget the experiences he had in the dreaming or otherwise.

The effect is similar to the idea of the Delirium that crinos garou and other fera induce, but without the madness that it sparks in humans. It is simply a forgetting of precisely what happened, wholly and completely.