You can add power to your spells or spell-like abilities at the expense of your companions’ health.
Prerequisites: Any one metamagic feat, moderate depravity.
Benefit: You can enlarge, extend, heighten, or widen a spell, as though you had the appropriate metamagic feat, without increasing the spell level or, for spontaneous casters, casting time. You can apply any number of these metamagic effects to a spell in this way; if you choose heighten, then that spell’s level is heightened by up to two levels.
For each level of metamagic you apply, one of your allies takes 2 points of Constitution damage. In this case, “ally” is defined as someone who knowingly and willingly fights alongside you against a common foe, or who otherwise considers you a trusted companion. You decide, when casting the spell, which ally takes the Constitution damage. You cannot select an ally immune to Constitution damage or an ally without a Constitution score. For purposes of this spell, you cannot designate a summoned or charmed being as your ally.
You can use this feat three times per day.
Special: You can select this feat more than once. Each time you do, you gain an additional three uses per day.
Source: Heroes of Horror, page 122.