The orb doesn't seem to be<em>expending</em>energy for any purpose, though he finds that he can easily tap into its power, and use it for casting spells, using less energy to invoke powerful spells. (Effectively, reduces the total level of a spell by up to 2, after metamagics are applied, but consumes power from the orb, equal to the unmodified level of the spell.)<br/><br/>The actual power being supplied to the orb seems to come from the basement, where a seemingly greater source of power is located.