Pale lavender ellipsoid

Pale Lavender Ellipsoid (Legendary): As a reaction, when you are attacked by or targeted by a spell of 4th level or lower, you can use the stone to absorb the spell without harm. The stone can’t absorb spells, such as fireball, that target more than you alone.
When the stone has absorbed 20 levels of spells, it burns out and turns dull gray, forever useless. If you are targeted by a spell whose level is higher than the number of spell levels the stone has left, it cannot absorb the spell.