[Galadriel55]

Um, Wormtongue?

Faithful I - as Gandalf said, for many years he served Theoden faithfully, as he could
yet I my lord betrayed
To serve the one who wielded shadow - aka Saruman
Shadow I helped defeat. - killed Saruman
Patient was I - gradually loosening Theoden's will and "poisoning his thoughts"
but rash move I made. - Maybe how he spit at Theoden?
Madness tore me - Killed Saruman when he was...pretty angry
now at last I
Know what it is to sleep. - well, he constantly had to be vigilant with his "master", be it Theoden or Saruman. When he died, it must have been something of a relief not to constantly be on the watch...