"Having put down a rising of giants, it was discovered that the motivating force behind their depredations was that of long-forgotten evil: the Dark Elves. Determined to seek out these creatures, a body of doughty adventurers mounted an expedition to learn the strength of the Drow and bring retribution to them."
What do I mean by Deep Ones?! The immortal frog fish men straight out of H.P. Lovecraft's The Shadow Over Innesmouth?! The Deep Ones are survivals straight out of mythological myth & legend with cities all over the oceans including Europe and that includes the swamps of Paris which was once one of their seats of power. They mean to have that particular center of power back and in Dark Albion they gain it during the Rose War.
All throughout the countryside the Frogmen's witch covens & cults have been sewing mayhem & evil weakening France. The Frogmen are in direct competition with the Dr ermm Elves for all of the marbles during the Hundred Years War. But God is not mocked & Dagon's brood are in for a rude awakening in the form of "The Maid of Orléans" (French: La Pucelle d'Orléans).
So not only is she and her forces instrumental for boasting the morale of France but she's instrumental in stopping the push by the Deep Ones during the Lancastrian phase of the Hundred Years' War.
Blibdoolpoolp might well be another chaos god avatar of the Deep Ones she has all of the required Lovecraftian elements & lends a large amount of weight to the encounter with her. She's an interesting contrasting chaos goddess symbol for various witch cults especially given the implications that the French population had not recovered to its size previous to the Black Death of the mid-14th century. This was a time when ripe for violence across the countryside.
PC's are going to have to bring their 'A' game playing through a Lion & Dragon campaign set up for Gary Gygax's D2 "Shrine of the Kuo-Toa" (1978) especially during the Lancastrian phase of the Hundred Years' War.