Possible Clues:

• Features of hedgehogs
• Books' backs
• They make wood prickly in the ship
• Backbones of books
• Quills; prickles
• Sea urchin's protection
• They point to the wood in the ship
• The way to start at the start of the month with the thing I swallowed
• The wood in the ship makes them sharp
• Are they sharp enough to make some deal among the saints?