Wall of Magical Exhaustion

A sickly green, transparent wall springs into existence at a point you choose within range. The wall appears in any orientation you choose, as a horizontal or vertical barrier or at an angle. It can be free floating or resting on a solid surface. You can form it into a hemispherical dome or a sphere with a radius of up to 10 feet, or you can shape a flat surface made up of ten 10-foot-by-10-foot panels. Each panel must be contiguous with another panel. In any form, the wall is 1/4 inch thick. It lasts for the duration.

When a creature starts its turn in the wall, or the radius of the dome, or enters for the first time on its turn, the creature loses a number of spell slots equal to a d4. The slots can be divided up as the creature chooses, for example, if a 4 is rolled, then the creature could discard 1 4th level spell, 2 2nd level spells, etc. If the creature has no spell slots left, or is not a spell caster, they take 3d6 necrotic damage. Spells cast through the wall or dome fail if cast at their lowest level. If spells are cast at a higher level, only the effects of upcasting succeed. For example, a 4th level fireball cast through the wall or dome would only deal 1d6 fire damage, not 9d6. The wall or dome cannot be targeted by anything except for Dispel Magic.

Casting this spell at a higher level at 7th level increases the spell slots drained by 1d4, to a total of 2d4, and casting it at 9th level increases the spell slots drained by an additional d4, for a total of 3d4.