This happened so fast that I didn't even realize what had gone wrong until I noticed that the Hydra was one hit point less than he should have been. Here's the screen shot. As you can see I was doing a 1HP challenge so there was no possible way I could have damaged him and as the battle log shows, he clearly charged and then took one crushing damage. So...I'm guessing he hit himself with his own charge. Somehow. Best guess is that it's because it's a large creature charging into a wall.
I've seen this before, it's because of which square of the hydra is looked at for charge. I'm pretty sure that depending on your direction, it checks to see if there's a figure in the next square of your charge and there is—another square of you. So you deal damage to yourself because you're in front of your own charge.
Logged this. 2x2 creatures need some love at some stage, mainly because I want them as playable characters in leagues.
