An excerpt from my Lamentably Not Brief Guide To The Levercastle Universe that I quite like. I hope you enjoy it too.
The Liminus weaves like a web throughout the realms, and is anchored by the Undone. The web is made of a thing called Liminal Spacetime (alchemists named it, don't blame me). More poetic souls have called these places the Endless Midnight, which is nice, but not as accurate, this is often the way in the war between alchemy and poetry. A good inbetween is just to refer to liminal places or times as Midnights.
Midnight is, in fact, an excellent example of a Liminal Spacetime event. People often argue about when Midnight actually is, after all at any given moment it's midnight somewhere in the universe, right?
Well, maybe if you're the type who gets their kicks being insufferable and smug, yes, I suppose. This doesn't mean that this evaluation of matters holds any actual weight.
You will know when midnight comes where you are, you will be standing in the middle of it. Not all midnights are the same.
It has to be said, however, that there is a certain common sort of midnight, we all know them, they come at midnight, as one day folds into the next.
A standard midnight has the effect of wiping away all loosely thrown enchantments of the previous day. Almost all enchantments get reset at this time. The effects of a transient enchantment, however do not; bad news if your house got crushed by a magic rock. Sorry.
Anything weaker than a standard midnight, e.g. crossing the threshold of a house, is only enough to achieve some minor effects low-grade changes in fortune, warding off of certain subsets of magical creature etc.
Low-grade Midnights may be combined or have their power boosted by events e.g. a house's threshold has more of an effect on New Year's Day.
The Midnight at New Year is an example of a magnified, more powerful Midnight. This will break stronger enchantments and confer widespread gifts of renewal over all caught within the area of effect of the New Year midnight.
Event anniversaries, such as birthdays, or the day one year after when a powerful enchantment was cast, are much stronger than a standard Midnight but not as strong as a New Year Midnight.
Some Midnights, such as those on Solstices or Equinoxes are stronger for certain people than others. Belief is a factor.
Thus it is true that Midnights can be manufactured, great arches can make super thresholds, stone circles can capture midnight within a space. Midnight energy loves to live in circles, doesn't mind triangles, will have some fun in squares, likes pentagrams for a change and will inhabit any other geometry by prior agreement (alchemists like nine-sided things, enneagrams, for no particular reason than just to show off).
Midnight energy, dispels, cleanses and can confer some minor gift or curse such as a change in fortune, health, romance or wealth. All races, even mortals, can get something from a midnight with obvious limitations.
The energy is ambient, it is something that anyone can use, like air or water. For this reason, although it affects magic and enchantment it is not really regarded as such. Really getting a big bang out of Midnight energy is something best left to alchemists and other magic users, the liminus has a short temper when it comes to being taken for granted, or abused.