* They're big. During a life span of less than two years they can grow to 7 feet long and 100 pounds, but they occasionally get far bigger: a 300-lb specimen was reported by Humboldt expert Scott Cassell.
* They're bad. They have razor-sharp beaks and their arms are covered with thousands of sharp barbs. They often don't try to kill their prey - they just latch on and start eating. They have been known to bite scuba divers and drag them down into the depths. They have killed fishermen who fell overboard. When a Humboldt is caught by a fisherman, hundreds of others may surround the boat - not to protect their captured colleague, but to try to eat it. Mexican fishermen call them diablos rojos (red devils).
* They're dangerous. They hunt cooperatively in packs of up to hundreds and can travel at 25 MPH. They have stereoscopic eyes (like us) and very large brains.
* They're weird. They have have a parrot-like beak, three hearts and blue blood. They can change color several times a second, from deep red to white. They prefer to hang out in the least-oxygenated part of the ocean where virtually nothing else can survive, but they can live at higher depths as well.
* There are a lot of them. Nobody seems to be willing to hazard a guess how many, but fisherman in California can go out and catch 200 in a few hours, essentially scooping them up until their boats can't handle any more weight. This California population explosion just started recently. On a worldwide scale, scientists believe that squids top humans in terms of total biomass.
* They're coming this way. Natives of South America, they recently colonized the waters off of California, but have been spotted as far north as Alaska. Their migration may have more to do with the over-fishing of their main predators/competitors than with water temperature.
Here is some cool video footage of Humboldt squid. I couldn't find any really grisly videos of Humboldts, but here's a video of an octopus killing a shark.
Is this all real? I think it mostly is - even though scientists seem to be bickering over details, and there's a fair likelihood that the California infestation is a transitory phenomenon. But I have to admit that yes, Humboldt squid are even more scary than man-eating clams. ;-)