Weave Cleave

As part of casting this spell, make a melee weapon attack against one creature the weapon used to cast this spell can reach. If this hits, the creature takes the melee weapon's normal damage, and their connection to the weave becomes partly severed and highly unstable for the spells duration. If the creature attempts to cast a spell during this time, they must first make a Strength check against your spell save DC to attempt to pull the weave temporarily back into order. If they succeed this check, the spell is cast normally. If they fail, the energy that would be spent on the spell explodes violently outwards in a 10 foot area, plus an extra 5 feet for every level of the spell they cast. All creatures (except the caster of the failed spell, which automatically fails) within that area must make a Dexterity saving throw against the casters spell save DC, taking 3d4 force damage per level of the spell they cast on a failed save, or half as much on a successful one.