Empower Spell-Like Ability( Book of Vile Darkness, p. 49)
The creature can use a spell-like ability with greater effect.
All variable, numeric effects of an empowered spell-like ability are increased by one-half. An empowered spell-like ability deals half again as much damage as normal, cures half again as many hit points, affects half again as many targets, and so on as appropriate. For example, a night hag's empowered magic missile deals one and one-half times normal damage (roll 1d4+1 and multiply the result by 1.5 for each missile). Saving throws and opposed rolls (such as the one made when a character casts dispel magic) are not affected. Spell-like abilities without random variables are not affected. Each of a creature's spell-like abilities can be empowered twice per day, though the feat does not allow the creature to exceed its normal usage limit for any ability. Thus, if a night hag chooses to empower its magic missile ability, it can use an empowered magic missile up to two times that day. Thereafter, it could use its magic missile ability again normally (since it can use magic missile at will), or it could corrupt another of its spell-like abilities, such as sleep.
This feat can be taken multiple times. Each time it is taken, the creature can apply it to each of its spell-like abilities two additional times per day.