Guthan the Infested

Guthan the Infested is one of the six Barrow brothers. He attacks with melee, and since he is obviously wearing his armour, his special effect is in place. This means he can heal himself at a 1:1 ratio. So if he were to hit a 20, he could heal himself for 20.

Nearly all players "tank mage" Guthan. This means that they will mage while wearing their melee armor, such as rune. Even though wearing metal while maging reduces your mage bonus significantly, there is no need to worry becuase Guthan's mage defense is so low you will hitting almost as high as with mystic or other robes. This strategy is used so he won't be able to heal himself as often. It is known that he can still heal himself through prayer. Though you won't sustain damage, he will heal for the amount he would have hit, had you not had prayer on.