"I cannot, for my soul, remember how, when, or even precisely where, I first became acquainted with the lady Ligeia. Long years have since elapsed, and my memory is feeble through much suffering. Or, perhaps, I cannot now bring these points to mind, because, in truth, the character of my beloved, her rare learning, her singular yet placid cast of beauty, and the thrilling and enthralling eloquence of her low musical language, made their way into my heart by paces so steadily and stealthily progressive that they have been unnoticed and unknown."
--Edgar Allen Poe, "Ligeia"

• The PCs' patron sends them a message telling that he no longer cares for the ancient artifact (or what have you) he'd previously sent to search for, and will no longer be financing them. When they ask why, he says he's found a new bride who's now occupying all of his time (and, the PCs gather, resources). If the PCs don't immediately find this suspect, the messenger himself is rather willing to note how odd his master's behavior has been. Is the PC's benefactor bewitched, or just in love?
• One of the PCs has an admirer. A powerful one. An enchantress known across the land as having the ability to bend lesser wills to her whim at only the slightest exertion of her talents. She may have worked for a friend or foe in past, but somehow saw her chosen PC in action. If the PC is flattered and accepts her advances, she quickly proves too commanding to be coexist with the PCs peacefully. Either way, after being rebuffed, she flees the city, and promises to ensnare her love's mind as soon as he leaves the protection of civilization.
• At a banquet, of the PCs meets a strange woman of peculiarly discriminating tastes, a keen wit, and a comely beauty. Soon after, she appears everywhere the PCs go: An old contact brings the PCs in to brief them on a new mission, and she's his research assistant; a nobleman friend of the party brings her as his guest to a ball; finally she appears in the PCs' own stronghold, and though none of them distinctly remember why, everyone's pretty sure she's supposed to be there. In any event, she's very helpful, as she seems to know everyone in the city. However, with every day that passes, the PCs feel more tired, older, less able-bodied. If anyone cares to check, the mystery woman has a history far too long for any normal individual of her species, and yet she still seems young and vital, and it most certainly not undead. What do the PCs do about this strange creature?