Barrier Technique

Create a 40-foot-radius inescapable barrier and imbue it with a spell of your choice. For each entity contained within the barrier, you gain 1 charge of the imbued spell at the start of each round. Charges may be spent at any time and only to cast the imbued spell. Casts made using these charges automatically hit their target. All unused charges are lost at the end of the round and are recalculated at the start of the next round based on the number of entities within the barrier. The barrier shares its hit points with the caster and may be targeted and damaged by attacks originating from outside the barrier. Any damage dealt to the barrier is applied directly to the shared health pool