A small slug like animal that is a member of the slug family. It is a parasite that attaches itself to any part of a warm blooded animal. It has small teeth on one of its ends. (the end with the eye stalks) and it uses this to open a wound into its host. Then a tongue like tentacle enters through the wound. They go through the body. From here it gradually grows through the eletrical impulses sent through the nerves of the host. It acts as a condutor for the eletrical impulse where it absorbs part of the impulse before sending it along its way.
It improves the reflexes of the host, along with giving it fast healing. Once it one of the tentacles reach the brain the host and the slurg become one mentally. If this happens in an intelligent victim, the victim’s IQ will increase. Unfortunately, this will lead to madness.
You can see tentacles spreading throughout the body of the host from the mian part of the slurg through the skin of the host. It is capable of sudden growth of special tentacles called barbs which it shoots out of the skin of the host and at whatever it precives as a threat to it and or its host.