......Sygian Spikes do MP damage, not HP Damage. basically for every hit you take, you absorb a certain amount of mp from the mob. For absorbtion effects, there is a damage number displayed on the target, and a regen number displayed on the caster. The colors for MP damage and regen should be different from the colors for HP damage and regen. And unless there was a ninja mod, damage decrease due to stoneskin or block does not affect the amount of MP absorbed, which is based off of the original damage amount. This was experimented with during the earlier stages of the game.