Elemental Wall

At 8th level, once per day you can create a wall of energy. You can choose fire, cold, acid, or electricity damage. An immobile, blazing curtain of the chosen energy springs into existence. The wall deals damage of the chosen energy type when it appears, and to all creatures in the area on your turn each round. The wall also deals 2d6 points of damage of the chosen energy type + 1 point of that type per caster level (maximum +20) to any creature passing through it. The wall deals double damage to undead creatures. At 12th level and every 4 levels thereafter, you can use this ability one additional time per day, to a maximun of 4 times at level 20.