Damn do I wish I was 2 levels higher so I could have my attacks treated as force effects.
This should certainly prove challenging.
If my estimates are correct, it should be really easy to hit, but only half our attacks will hit and even then it's got Fast Healing 22. That's... pretty good. It wouldn't be able to hit us as easily at a living hydra, but considering its 12 heads are touch attacks, its low dex score and 1/2 BAB isn't going to matter.
With my high touch AC, there's a chance he might not even be able to hit me without landing a crit (and knowing Phaedrus's rolls, it will), and I'm currently medium size so I don't take the same penalties on AC or attacks that I normally do. If we fight it, I should definitely be front line, so I better hope I get a high Initiative. Anyone else who doesn't have a good touch AC (or mage armor) should stick to the back, out of its range.