Arcane Guard

Creates a magical guard in a 5ft square, which looks like a skinny tall humanoid fully covered in armor with a lightning whip. If anyone casts a spell in the 30 feet radius of the guard, it immediately dashes to the target and hits it with a whip. It uses your spell attack modifier and delivers 4d6 lightning damage. Ward disappears after an attack. Ward has an AC of 18 and HP of 20. It has immunity to all conditions but fails all saving throws.

At Higher Levels. If you cast this spell at higher level, ward will not disappear after an attack and will stay for one more trigger for each spell level slot used above 1st. It will also gain 5hp for each additional level. Guard attack can't be triggered more than once per round.