This is a Monster — a class feature gained through that class's own talent choices, not a feat you pick through normal feat selection.
Choose one of your spell-like abilities, subject to the restrictions described in this feat. You can use the chosen spell-like ability as a traumatic spell-like ability three times per day (or less, if the ability is normally usable only once or twice per day). When you use a traumatic spell-like ability, affected targets must succeed at an additional Will saving throw the next time that they sleep (DC = the spell-like ability's DC) or be affected as per nightmare. Each time the target fails its save, it must save again the following night or be affected by another nightmare, though the save DC decreases by 2 each night after the first. This feat can be applied only to spell-like abilities with the emotion or fear descriptor. Targets that avoid the spell-like ability's effects avoid this feat's effect as well. You can only select a spell-like ability duplicating a spell with a level less than or equal to 1/2 your caster level (round down) - 2. For a summary, see Table 3-1 on p79. [Special] This feat can be taken multiple times. Each time it is taken, you are able to apply it to a different spell-like ability.
Prerequisites
Spell-like ability at caster level 6th or higher