Ioun Stone of Absorption

{c}Requires Attunement
While this pale lavender gem orbits your head,
you can use your reaction to cancel a spell of 4th
level or lower cast by a creature you can see and targeting only you.
Once the stone has canceled 20 levels of spells, it
loses its magic. If you are targeted by a spell
whose level is higher than the number of spell
levels the stone has left, the stone can't cancel it.
The stone has AC 24, 10 HP, and resistance to
all damage.