Cage of elements

Depending on the elemental affinity (affinity meaning a majority of 1 elemental spell) of the caster, the cage takes on the form of that element, if the caster has no affinity it takes on the form of all elements. cast at level 1 the bars deal 1d6 damage based on the element of the bar. every level higher until level 4 deals an extra d6 of damage.