Might Stone

This smooth gray stone features a round black depression on its surface. You gain a +2 luck bonus on saving throws against spells and spell-like effects. A spontaneous caster (bard, sorcerer, favored soul, and so on), a character who uses invocation (dragonfire adept or warlock), or a psionic character can invest a known spell, invocation, or power into the might stone, temporarily removing it from his knowledge for 1 day. For a number of times per day equal to the spell level invested, you may, as a swift action, activate the might stone, gaining any one of the following features.

• Increase the save DC of a spell or power of the same school or discipline by +2.
• Add an extra 1d6 points of damage (of the same type) to an eldritch blast or breath weapon.
• Gain a +2 bonus on checks made to overcome the spell or power resistance of a target creature.

Imbuing the spell takes a minute of concentration You may imbue just one spell into the might stone per day.
strong; (DC 22) transmutation, CL 15th; Craft Universal Item, Craft Wondrous Item, bestow power, spell matrix; 14,400 gp, 1,152 XP. Weight: 1 lb., 28,800 gp.
Source: Dragon #356