Don't really see how thematically he loses 1 health. Perhaps you could make his ability called "Axe grind" or "Axe sharpen". That would make more sense as he'd be sharpening his axes (increasing attack), and he could also hurt himself in the process (axes are sharp). As for whether it's overpowered or underpowered, it's quite fine as it is. You're paying 7
for a 7|5 creature. Compare that with Shrieker which is 8
for 8|3.