This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Lyngbakr ( Greenland)
Lyngbakr (Icelandic, lyngi "heather" + bak "back") is the name of a massive whale-like sea monster reported in the Orvar-Odds saga to have existed in the Greenland Sea. According to the saga, Lyngbakr would bait seafarers by posing as a heather-covered island, and when a crew landed on his back, he sank into the sea, drowning the crew.
Both the lyngbakur and hafgufa seem to have derived from a single creature called the aspidochelone in the Physiologus. The Icelandic Physiologus contains two illustrations of the aspidochelone, one with its back overgrown with vegetation and another with gaping jaws.