Cleon
Legend
Since it's a magical hybrid, it should be a magical beast, not an animal.
Yes, I wondered about that, but "Magical beasts usually have supernatural or extraordinary abilities, but sometimes are merely bizarre in appearance or habits." and the Elite Giant Rats' abilities don't include anything that would be unusual for a mundane creature.
Come to think of it, all I've got on their origins is that they're a "crossbreed" that was "specifically bred by Greasel Greedigutt". I don't actually know whether said Greedigutt is a spellcaster, they could have been created using some kind of genetic splicing.
Besides, I wanted to make them Dire and it's less of a stretch if it's an Animal.
So, I'm leaving them Animals for the time being, but will change "magical hybrid" to "strange crossbreed" and leave their provenance unstated.
That said, if Shade or Freyar fancies them being Magical Beasts too, I'd be happy to change them since I'm not 100% decided on the Type. Of course it'll make them a little tougher in the process, which is not to be sneered at...
It's just a matter of 3d10+6 hit dice, 22 hit points, +3/+7 BAB/Grapple, +7 bite & +2 claw attacks and tweaking the Dire SQ to a "Dire Beast".
Updated.