Randall Flagg has appeared in Dark Tower.
Randall Flagg . He has a variety of names , usually with the initial letters `` R. F. '' but with occasional exceptions , such as Walter o'Dim ( originally envisioned by King as a separate character ) in The Dark Tower series . The Dark Tower expanded on Flagg 's background and motivation , linking his previous appearances . He has also appeared in Marvel Comics ' adaptations of The Dark Tower and The Stand .