Wall of Ice
A wall of ice spell creates a huge wall of ice, with a front face of up to 100 square ft per level. Its exact dimensions are adjustable by the caster. Thus, if the wall is cast by a 20th level caster, the dimensions of the wall could be any combination of dimensions that multiply to equal 2,000 square ft. The wall might be 10 ft high and 200 ft long, or 5 ft high and 400 ft long, or 20 ft high and 100 ft long, etc. The wall need not be cast so that it is attached to anything, and it can even be cast in the air to fall upon opponents, doing 3d10 points of damage in the area where it falls. Breaking through the ice with a melee weapon causes 2 hit points of damage from ice shards per inch of thickness, and can be broken out at a rate of 10 ft per round. Normal fire has no measurable effect upon the wall, but magical fire will melt through it in one round. If the wall is destroyed by fire in a single round, it will cause a massive cloud of water vapour to form and linger for a full turn, obscuring vision by 50%.