A mi-go's claws are capable of swiftly and painfully performing surgical operations upon helpless creatures or those it has grappled. When a mi-go makes a successful grapple check, in addition to any other effects caused by a successful grapple, it deals sneak attack damage to the victim. A creature that takes this damage must succeed at a DC 18 Fortitude save or take 1d4 points of ability damage from the invasive surgery (the type of ability damage dealt is chosen by the mi-go at the time the evisceration occurs). The save DC is Dexterity-based.