Rose Madder is Mordred Deschain.Or rather a Twinner to him, on some other level of The Dark Tower.
- Can a being like Mordred have a twinner though? There seems to be only one Randall Flagg after all. Also, Rose Madder seems to be on the 'Cosmic Order' side of the alignment spectrum.
Rose Madder is a creature similar to IT. Both tend toward arachnid forms when not needing a less alarming disguise and both have true forms that drive a human viewer insane.
- Which has interesting implications itself, since Rose Madder seems to be more or less on the light side cosmically speaking.