Ring of Wizardry

Adds +2 To Hit on Spells (not scrolls or items) requiring a combat slide. A Spell affected by this ring deals double damage if a natural 20 is scored. If that particular Spell has additional damage bonuses, those bonuses are doubled as well.

This ring cannot double a Spell’s damage on a creature you cannot critically hit. This includes, but is not limited to creatures without a vital anatomy, Constructs, incorporeal creatures, Oozes, Plants, and Undead. However, if you are able to overcome a creature’s crit immunity, the double-damage ability of this ring is effective against that creature.

Note: Any time doubled damage gets doubled again, the end result is triple damage (×3), not quadruple damage (×4)