Planarian

The Planarian is a non-parasitic flatworm with the ability to regenerate lost body parts regardless of how it's cut; each separate part will in turn become it's own individual. Planarian also have the ability to produce and glide along mucus that could otherwise be used against enemies. Larger summons can spew enormous amounts of water from their gullet as well as ingest people with intent of safekeeping or harming them. Using their ocelli they can detect even the faintest of light in the darkest of areas which is beneficial for tracking missions or fighting in darkness. To fight them underwater could mean death simply due to how difficult it would be to destroy them and deal with their numerous abilities.