The only person to ever take Casterly Rock was someone called Lann the Clever. According to legend, Lann broke into the Rock by squeezing himself through a narrow, secret entrance. As Martin wrote in ‘The World of Ice & Fire’: ‘Once inside, he began to whisper threats in the ears of sleeping Casterlys [the family that lived there at the time], howling from the darkness like a demon, stealing treasures from one brother and placing them in the bedchamber of another, rigging snares and deadfalls. Thus, he set the Casterlys at odds with one another and convinced them their seat was haunted.’ Lann then took the castle for himself.’
Part of course:
Why Casterly Rock Matters So Much to Tyrion Lannister (Vanity Fair)
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