What are whitby wyrm dragons?

Whitby Wyrm, a dragonlike serpent that has inspired much art such as posters, T-shirts etc. The story goes that during the building of the Whitby Abbey the great fire-breathing Wyrm was disturbed from his slumber in the mountain. He attempted to destroy the town but was banished into the sea. Every seven years he returns at full moon to attempt to drag the abbey into the sea by clawing away at the cliff on which it stands.