Karamthulhu are a squid-like species that are sometimes obtained while fishing for slugs during the Rum Deal quest. They are also dropped by Zombie pirates and Zombie swabs.
Karamthulus can be used in addition to Sluglings to make Unsanitary swill. After the quest, any Karamthulhus remaining in inventory will disappear, and an attempt to fish for them triggers the response, "You have no need to do that any more."
Previously, if you tried to use an alchemy spell on it you would get the message, "You cannot cast alchemy on your follower!"
A glitch was discovered involving Summoning a Karamthulhu on 12 January2008, before Summoning's release. When you died with a Karamthulhu, it would briefly appear as an NPC. The glitch was fixed the same day. The glitch had apparently been around since the Rum Deal quest was released. This had been mentioned on a Summoning Development Diary that they knew this glitch was in the game, but not many players had found it, or paid any attention to it.