Helm of Brilliance

This helm is set with 1d10 diamonds, 2d10 rubies, 3d10 fire opals, and 4d10 opals. Gems removed from the helm crumble to dust. The helm loses its magic when all the gems are removed.

While wearing this helm, you gain the following benefits:

* You can use an action to cast one of the following spells (save DC 18) with the listed gem as its component: daylight (opal), _fireball (fire opal), prismatic spray (diamond), or wall of fire (ruby). The gem is then destroyed.
* If at least one diamond remains, the helm casts dim light in a 30-foot radius if at least one undead is within 30 feet. Any undead that starts its turn in the light takes 1d6 radiant damage.
* If at least one ruby remains, you have resistance to fire damage.
* If at least one fire opal remains, you can use an action to speak a command word and cause a weapon you are holding to erupt in flames, causing it to deal an extra 1d6 fire damage on a hit. The flames cast bright light in a 10-foot radius and dim light for an additional 10 feet. The flames last until you use a bonus action to speak the command word or you release the weapon.
* Whenever you fail a saving throw against a spell and take fire damage as a result, roll a d20\. On a 1, light blazes from the remaining gems. Each creature within 60 feet other than you must succeed on a DC 17 Dexterity saving throw or take radiant damage equal to the number of gems in the helm. The helm and the remaining gems are then destroyed.