Elemental Resistances

At 100 resistance, you will take normal (100%) damage from elemental attacks. At 0 res, you will take 200%. While at 200 res the attacks will do no damage, increasing it above 200 will mean you get healed from such attacks.

It is possible relatively easy to get res 200+ by using a shield with high elemental resistance. The benefit of doing this is that a player doesn't need to dedicate his entire setup of gear to the resistances, but can simply raise his shield when confronted with an elemental attack, which now heals him inbetween making attacks himself.