Meditating on Japanese ghosts and monsters.
A haunting that appears only in moonlight: a gallows that shows a swinging body in moonbeams, a wailing specter who appears when the light of a summer’s crescent moon filters through the window of the kitchen where she was murdered. Could be the critical clue to solving a mystery, especially if the Dead can be contacted through this means or released from their prisoning.
Or even artificial light:
A character has performed an unjust murder (yes, I know, by the definition of the word “murder” it’s inherently unjust). They are followed by the face of the deceased popping up in unexpected places, and ordinary objects become suddenly sinister. Roots coil and strike like snakes, a ragged lantern becomes the harrowed face of the victim, the character’s reflection is transformed in unpleasant ways. Your option as to whether Remove Curse actually works, but I recommend making a proper atonement (no, you can’t just cast the spell, you pussy, go and fix the situation you created) instead. Suicide is the most effective atonement.
Something the PCs have saved, spared, or otherwise aided takes a beautiful human form to thank them. That Way. Imposes a fairy-tale condition on their new lover (no looking at me at night, whatever). If broken – and it will be – they revert to their former form and leave without regret. Any children will be human, but.. weird. One of many sources of wizards, especially when Foxes are involved.
There’s also the classic “This traveller is not what he seems – look at his reflection! Iron mirrors break Fey Glamours, Silver the illusions of the Undead, bronze the charms of the kitsune. Pure running water’s reflection destroys all charms
Bad Things happen when people are raised from the dead. Again, fairy-tale conditions apply.
Cannot touch dead flesh, or their animus leaks into it, diluting their soul, decaying them slightly, and briefly animating the meat.
Anyone with True/Second/Death Sight sees the person as a horrifying, shambling corpse.
Cannot sire children (I automatically impose this one anyway).
The character is only raised for a set time, or based on a set condition; a year and a day is traditional.
The character cannot go abroad on the night of their death, or the Furies will arrive to scourge the soul from their shell and take it back.
The Character has become a hollow shell, who must feed on the energies of the dying or fade away again into the Abyss.
Always surrounded by babbling, phosphorescent, or fearsome spirits.
Pictures 1, 2, 5, 6, and 7 by Yoshitoshi Taiso. Picture 4 by Hokusai Katsushika. Picture 8 by Maboroshi Chouji. Source of image 3 unknown.