Physical Description & Attributes
As the name implies, the Cthulhu Creature bears a resemblance to the ancient, fictional entity Cthulhu, an alien god temporarily imprisoned under the sea. The Cthulhu Creature appears as a humanoid with several long tentacles that extend down mid-torso, from directly above its mouth and below its nose. Its hands also seemed much larger than an average humans, and appear to be either mutated of some sort, or the creature is wearing gloves. Its skin is a pale grey-green color and it wears ragged grey clothing and large boots.
Assuming that it is based off of the original Cthulhu, it is possible this creature possesses some supernatural psychic abilities, such as telekinesis and telepathy or some dark magic, although this is speculation. The canonical Cthulhu was the size of a mountain, so this incarnation is some derivative being, possibly a servant or worshiper. The presence of clothing seems to indicate that it was formerly human.
It is not known what item summons this monster. It is possible that some artifact mentioned in the story it is based on, The Call of The Cthulhu, will summon it; it is equally possible that reading the story itself summons it.
The Cthulhu Creature appears in its cube, and in the behind the scenes footage for the film.
Given the name of the creature, it's a reference to the story "The Call of Cthulhu" by H. P. Lovecraft, and more likely a reference to The Shadow over Innsmouth . There were also many horror films base on H.P. Lovecraft's work such as In the Mouth of Madness, Call of Cthulhu, From Beyond, etc.. It is also possible that this creature could also have been based off of Davy Jones from Pirates of the Caribbean, due to the crab claws and tentacle mouth. There is also a notable resemblance between this monster and an Ood, a creature from the Doctor Who universe.