Amulet of Vicious Protection

Amulet of Vicious Protection
Wondrous Item, rare, (requires attunement)

A purple amulet that once attuned can be used to create a forcefield in a 10ft sphere in any location. This sphere is concentration. Once created, the sphere cannot be moved. All creatures within this sphere cannot be damaged from outside of the sphere. When the sphere is broken by exceeding the forcefield's hit point maximum, the caster must roll a d20 and add their casting modifier. (If they aren't a caster, use wisdom). On a natural one, the shield breaks and deals 25% of the damage taken in a 10ft radius. On a 1-5, the shield breaks and deals 25% of the total damage the shield has taken at the target who did the damage that broke it. On a 6-9, this number is 50% On a 10-15, this number is 75%. On a 16-19, this number is 85%. On a 15-20, this number is 90%, on a 20+, this number is 100%. On a natural 20, add your casting modifier and multiply it by ten, then at that number to 100 and that is the percent of damage. (Ex: WIS: 3, 3x10 = 30, 30+100= 130, 130% damage.) When the user loses concentration or drops the sphere, 100% of the total damage the shield has taken is sent back at a target or targets of the user's choice. The health of the sphere is 10+ the user's casting modifier. All damage dealt by this shield is magical. However when concentration is dropped the user can use to keep the type of damage or use force.
 
At Higher Levels
For every level gained while attuned to this item, the health gains an extra 10+ casting modifier. If your casting modifier is increased between levels, do not add your new casting modifier to the old health. At 3rd, 6th, 9th, 13th, 16th, and 19th level, this item gains an additional charge