Fortified Position can be used to be a kind of Corrode Barrier also. Sit on a Fortified Position with no other armor, take two Corrode, move away and back and no more Corrode. Takes an action that might be better spent, but if you have the time or need to save mana and have nothing to melee attack... this might be interesting. It might be interesting using a couple of these (in different zones, of course) with unarmored creatures on the move along with shift enchantments as has been mentioned elsewhere. Get Corroded, move out to another zone with a Fortified Position, and you still have your armor and the Corrodes go away.