Lonkeru

The Lonkeru, also known as tentacle weed, is a underwater plant growing only in the depths of The Blue Bay. Far down in the waters between Tam and Rashor purple tentacles grow from the bottom of the sea many hundred meters high. Possessed by some kind of energy or ancient power the arms sometimes reach up, attacking ships and pulling them down to the sea bed.

Origins

Not much is known about the origins of the Lonkeru. Shortly after the first humans arrived in Tal'Lyra the first tales about mysterious arms reaching from the bottom of the sea were told. Because the dwarves never were a seafaring people, it is not clear since
when the strange plant has been alive. But many scholars are of the assumption that the tentacle weed exists since the beginning of time. Some theories are concerned with the possibility that, because the Lonkeru only grows in the middle of the blue bay, it has magical origins and is protecting something deep under the sea level. The fact that the plant lies dormant for most of the time and only appears to activate for short random periods seems to support that theory.

Discovery and Research

While even the earliest sailors told stories of bizarre arms ambushing ships in the cove, it was believed for a long time that it all was just nonsense. Only after a ship of the Holy Order of Ras was attacked in the bay, the scholars and wizards became alert to the dangers of the ocean. First believing the purple arms were the result of some kind of druidic ritual, performed to weaken the talian trade routes, the blue bay was avoided for the rest of the age of war.
Following the end of the war of the two empires, the humans assumed the danger gone and started to sail the cove again. When the first stories of ships being attacked by tentacles started shortly after, it became clear that the evil under the sea was no dwarven incantation. The wizards of the holy order set out to tame the strange plant, securing the passage to the important harbor towns. Doing what they do best, a crew of twenty powerful order members was sent to destroy the Lonkeru. While it is not known what exactly happend to them their ship was never seen again.
Since it was apparent that the tentacle weed could not be destroyed, a new expedition crew was selected to dive deep down into the ocean and research the origins of the plant. Many hundred meters under sea level, they found the base of the Lonkeru. It appeared as all tentacles grew from one spot, as if they were guarding something. Being unable to get closer to foot of the tentacles, it was decided that other actions needed to be taken.

Measures against the Lonkeru 

The researching wizards noticed that the arms seemed to avoid their magical light, moving into the shadows. So for a long time every ship sailing in the bay was accompanied by a member of the holy order, guarding the vessel with his magic flame. Only when the idea of a enormous light house arose a permanent solution was found.
On The Watchers Island near Tam the light house was build and enchanted with an endless flame, shining onto the ships in the bay and protecting in from the tentacles and other dangers. For a whole millennium the magic light guarded the trade routes through the bay. 

The situation today

Following the destruction of the eternal light house and the downfall of the holy order sailing the blue bay had once become a dangerous endeavor. Most captains avoid the cove, unless they can sail near the coast or if they are wealthy enough to pay a wizard to escort their boat. Only the most daring and bravest ship crews dare to cross the bay and still some of them fall victim to the Lonkeru.