Giant Portuguese man-o-war

The giant Portuguese man-o-war was a species of monstrously sized aquatic creature similar to a jellyfish, though unrelated.

Description
These creatures had largely transparent bodies, which were difficult for most creatures to detect unless they could perceive invisible objects. They typically sported around ten to forty tentacles, with their length varying depending upon the specimen's size.

The smallest specimens were  in diameter and typically had ten tentacles that each measured  in length. The largest specimens were in diameter and typically had forty tentacles that each measured  in length.

Biology
The tentacles of these creatures were coated in a paralytic poison. They used this to stun their prey for easier meals. When tentacles were sliced off it did no harm to the central body of a giant Portuguese man-o-war and the tentacles would regenerate over the course of several days.

Ecology
Giant Portuguese men-o-war were known to live either solitary or in groups of up to ten members.

Habitats
These creatures were primarily found in warm oceans. In the Realms, they were only known to inhabit the seas and ocean around the Moonshae Isles.

Usage
Some sahuagin would place these creatures within their lairs to act as traps against any would-be intruders.