King's Field Episode IV: Epilogue (X) is an unordered open ended series (with no games completed or in the works) set in an alternative multiverse devoid of magic chronologically set after the events of game IX of the King's Field Episode IV: A New Hope cycle.
After IX the Dark Slayer is shattered into shards taken into the possession of the vampiric immortals. Without these magical shards of the black sword the immortals will cease to be. The Moonlight Sword is not present at least up to the time of Sword of Moonlight: King's Field Making Tool, after which games are allowed to resurrect a techno Moonlight sword somehow owing its existence to the rise to ascension of Sword of Moonlight software.
Instead Excalibur is featured prominently in the series. It reappears in the world sometime around the period of the legendary King Arthur, but appears to be devoid of magic. But in the presence of the shards of the Dark Slayer everyday items take on magical qualities permitting interaction with magical fields.
Due to the requirement that logic be absolutely consistent, a multiverse is a predictable outcome. They are a feature of the series. Logically each game takes place in a different (but not dissimilar) universe; in theory the universes of the multiverse do exert a degree of influence upon one another. Millia and her lover Alef survive IX. Alef clings to what remains of the Dark Slayer, a broken sword, with the single largest shard attached. Together they appear to be the most powerful immortals, however Millia takes pride in being the mother of the new age, and Alef though technically a man, is a man of a forgotten age. Physiologically different in every way. Just the same Millia is a changed woman. But a woman nonetheless. While sympathetic to the plots of the vampyric immortals, if necessary the couple will intercede to maintain the new order.
Between the two there is a heavy sense of duty to keep the fire of magic alight so that it may be called upon on those days where uncompromising logic threatens the very fabric of existence.
Settings should be modern, historical, or futuristic. The game should begin with the premise that magic, and monsters etc., is not an everyday occurrence, or a matter of occult happenings. But games can explode in a cataclysmic way if necessary. The multiverse structure allows for this. Other games may be more cerebral, and less action oriented, than the original King's Field games. Eg. mystery, suspense, and other kinds of less gamey genres. Especially decidedly dime store, or pulp, varieties.
Millia and Alef should not be featured in most games. Immortals may speak of them. Playing the role of either is strictly verboten (colloquially they are referred to as Mother Nature and Father Time.)
The timeline is historical, however there is a question of the origin of the universe. If the age of magic ended, did its universe disappear? Or is/was it part of another dimension? Well no. But time travel can be a theme in X games. Although how time works in this series, is it moves out in all directions geocentrically. In other words evidence of the age of magic was erased in all dimensions including time. Such that the Big Bang event was the last, and not the first, spectacle to herald the new age.
Excalibur is the original form of the swords Frostbite and Firebrand as it was bequeathed to the first Black Dragon along with the title given to the king of the Four Dragon Kings during the age of dragons, an earlier period of the age of magic.
Two volumes define the limits of X in relation to the overall project space. These are not numbered, but do implicitly come first (Malcom's Curse) and last (Laplace's Demon) by virtue of dealing with X events that cannot come earlier in the first case, or later in the last's. (The titles' apostrophes exist by pure chance; but nevertheless befit two weighty King's Field treatises.)