And to think I had originally cut the decapus from the rulebook! I ended up with some room on that page, added it back, and decided to give it an upgrade. It's now a beholder-style threat, but for lower-level characters. Probably my favorite monster now.
I'm thinking a group of level 2 characters could maybe take this guy on. He's going to attack with the tentacles for sure, but he's also got a few magical tricks up his sleeve... er, tentacle.
I like the idea that he keeps shifting his weight all the time, and attacks with a different number of tentacles each round; he's got 9, and 1d4+3 of them are attacking at any time.