Eos

Eos is a large, slime-like creature. Its body is like water balloon, behaving like a fluid with a heavy surface tension that can be broken with enough force, or if it chooses to let something pass. Its body acts as a gateway to an extradimensional space that it is essentially parasitizing, making it larger on the inside. Matter that vanishes into its body will float around in that space, increasing its size on the outside as if displacing a liquid. Objects within its body can be stored and moved around or removed later, or they can be broken down to permanently add to its mass. It is unknown if there is a limit to the size that it can gain by absorbing enough matter.

Eos can open up a "mouth" to expose the black hole in its head, using the immense gravitational force to pull things into its body. It is capable of manipulating its physical form however it pleases. If its surface its broken and not resealed for an extended period, its mass will start to leak away, evaporating into an ethereal haze. This can result in objects stored in its body being permanently lost in extradimensional space outside of its control.