For the genesis of Mikelmerck see Drama, Dice and Damsons. Rosey and I have batted ideas back and forth about this setting for old school gaming for a little bit. It would be a good setting for Lamentations of the Flame Princess, or (with some adjustment) Small but Vicious Dog. We envisage that PCs are the kind of loveable losers that 3d6 in order produces, and the setting sort of wrote itself. PCs are oddballs, fortune-hunters, ne're-do-wells and rogues. If not then they are stupid and rich (and those ones are usually clerics).
The "Great Marchland" as its name translates to (not "The March of St Mikela", as some effete southern scholars would have it) is often given such appellations as "True North" and "God's Own Duchy". The latter, incidentally, is where the confusion with St Mikela crept in; as theologians will know, this feminine spirit is the Voice of the Head, and thus misguided schoolmasters Down South thought they were very clever to link this to Mikelmerck's nickname. The real root of it is that Cushboth Himself would be at home in this paradise on earth, if he didn't like it, then stuff 'im.
Much as people take pride in this godliness, there are still rites to the ancient powers of earth, some of which have no name bar a title, powers such as the Nine Men of Muriz, and the Drowned Ones of Sevenwaters. As well as these, Mikelmerck has the dubious honour of being a place of dimensional 'thin-ness' - the barriers between otherworldly realms are weak here, and many tales are told of kinsfolk vanishing and reappearing years later, stark mad. The folk rites of the common populace (so scorned by the gentry) are designed to act as seals against these incursions from the realms of the Fey.
For humanity, this would be nothing short of a living nightmare, the very touch of a Fey Lord is enough to warp the body or chain the spirit. Their presence alone would begin to turn this world into another version of theirs, one of constant change and mad whimsy. Fortunately for most people this remains undreamt of as they retain only enough of the ancient prohibitions to enact them, not understand their real purpose. For those few magicians who know the truth, each new piece of knowledge is like the opening of a small leygate into their brain, leading most to be somewhat touched.