Island giants varied greatly in their appearance, but all were horrific. They were humanoid in shape, possessing bestial features that could include tails, horns, monstrous appendages, and a single cyclopian eye.
These behemoths on average stood 18 feet (5.5 meters) tall and weighed around 8,000 lb (3,600 kg). They usually dressed in rags crafted from the sails of ships they had wrecked.
Female island giants had an innate ability to shapechange into any human or humanoid form at will. They typically selected the form of a beautiful giant or human female as their form. They used this ability to find a mate and lure prey to their death. When in giant form, females were just as adept at males in tossing and catching boulders.
When young an island giant was capable of breathing underwater. They used this to flee from danger, including the anger of older giants.
Like many giants, island giants were adept at tossing boulders. They used this skill to deter anything from following them and to sink ships. They were also skilled at catching any similar objects thrown in their direction. Since they were not skilled craftsmen, they used their fists for close combat.
Island giants enjoyed luring ships into carefully placed traps so that they could feed for an extended period of time as opposed to just sinking a ship outright.
Their hatred for others, including their own kind, led island giants to lead solitary lives.
Island giants were a curiosity from a natural standpoint. The males were completely infertile, while the females were quite fecund. Females could breed with any human, demihuman or humanoid race, though true giant species were preferred. Because female island giants were just as hideous as the males, they took advantage of their shapechange ability to deceive their mates. Mating with a female island giant was a dangerous venture for the male since the female always attempted to kill and consume the male after the deed was done.
The average female island giant gave birth to 3-12 young per year. The young fled for the sea as soon as they were able. Those who stayed near their mother for too long risked becoming her next meal. Because of the violent nature of their lives, an estimated 1 out of 50 young island giants survived to reach adulthood.
Young island giants spent the majority of their time prior to adulthood living under the sea. When they eventually made a permanent return to land, males sought their own territory while females began the search for mates.
As omnivores, island giants ate anything they could, including seaweed and the bodies of beached whales. Live food was preferred, prompting them to attack any passing ship. If well fed, an island giant could live for a millennia.