This silver ring seems to smolder with an inner heat.

A ring of mystic fire provides a boost to your fire-based spells. When casting spells with the fire descriptor, you gain a +1 competence bonus to caster level.
This is a continuous effect and requires no activation.
In addition, this ring has 3 charges, which are renewed each day at dawn. Spending 1 or more charges grants a bonus to the amount of damage you deal with the next fire spell you cast before the end of your turn. (If the fire spell doesn’t normally deal fire damage, this expenditure has no effect).
1 charge: +2d6 fire damage.
2 charges: +3d6 fire damage.
3 charges: +4d6 fire damage.

Prerequisites: Forge Ring, fireball or flame strike.
Cost to Create: 3,500 gp (plus 500 gp for base item), 280 XP, 7 days.