Dereos Magic Dome

You create a 10-foot-radius, 20-foot-tall dome of magical energy centered on a point on the ground where the caster is stood. Glowing runes appear wherever the cylinder intersects with the floor or other surface.

Spells cast within the Magic Dome counts as 1 level above the expended spellslot up to level 6. This effect can be reversed to make spells cast within the dome to be 1 level below the expended spellslot.

If a caster is within a dome which diminishes the spellslots level by 1 when they cast a 1st level Magic Missile, they must make a DC 12 check corresponding to their Spellcasting Ability or the spell fizzles off into nothing.

 At Higher Level: Casting this spell at 5th level will increase the level of a spell cast within the dome by 2, to the limit of level 8. Diminishing Dome decreases the level by 2 and the DC is increased by 4.