I've been thinking a great deal about the political organization of Feywild civilization in my intended game, in the interests of getting a narrative grasp on the motivation behind the war. And I'm not a fan of the standard "seelie vs unseelie" divide, because binary monothic power-blocks of "us vs anti-us" is just too... Stalinist for my liking.
I'm thus picturing Feywild politics being based on ritualized exchanges of blood and power, wherein each participant temporarily gives up a portion of power over their own magical-dominion, in exchange for a momentary power over the other's later on, as well as a bond of alliance in times of adversity. Fey powers would thus form into Courts bound by interrelated pacts of blood and power, and there would be both major and minor Courts in play.
At present, I'm imagining the three largest / most powerful Courts to be the Court of Stars, the Court of Flowers, and the Court of Blood. The Court of Stars take the role of fate-mongers, with powers of prophecy, probability manipulation to get their prophecies to come true, and general temporal manipulation; and are led by the Lord of the Stars, a cold calculating son of a bitch who prides himself on being endlessly clever, both in the convolution of his schemes and in his wordplay. The Court of Flowers take the role of hope-salesmen, using emotion control, memory modification, and spatial manipulation to pull miracles out of their hats; their ruler is the Sun Lady, an arrogant and impatient monarch who prefers to just smash through the mental defenses of anyone standing in the way of the most aesthetically pleasing solution to a given problem.
And then there's the Court of Blood, who take the role of the wild hunt, using shapeshifting, physical augmentation, and summoning / control of beasts to chase down the enemies of Faerie. The Blood Court's ruler is the Blood Lord, an endlessly patient hunter who stops at nothing once the cry for havoc is given.
Until the Blood Lord is killed by a younger, more dynamic hunter, who believes he had not done enough to remind mortals to fear the wrath of Faerie. The newly-crowned Blood Lady is eager to distinguish herself from her more stolid predecessor, and so she has launched a crusade against mortal prey too clumsy (either physically or magically) to plausibly stand in the way of a resounding victory for the glory of her Court.
She is definitely a more Chaotic influence on her mostly-Lawful-Neutral peers, and there's more than a bit of selfish Evil in her agenda, but I don't want her to be the "villainy for villainy's sake" of a thoroughly Chaotic Evil monarch. So in addition to the obvious benefits to patriotic morale to be gained by a resounding military triumph, the Blood Lady's crusade requires a further justification which the other Courts can support.
Thus I need a prophecy with disastrous implications for the Faerie Courts, the early omens of which can be plausibly-enough seen in the recent past of the human nation in question. So that the other Courts can fear the Blood Lady's interpretation enough to be willing to support her Wild Hunt against those mortals (including the PCs)
Bonus points of course if the latter omens arise from the crusade itself, so that foiling the Blood Lady is actually what is needed to avert the prophecy. Because I would like to set her up to be a properly climactic campaign-ending boss monster, without the heroes being cast into a xenocidal role in their moment of grand triumph.
Any suggestions?