Master Slayer

At 20th level, an imitator becomes a master at studying his enemies to efficiently slay them. As a standard action, the imitator can make a single attack at his full attack bonus against an enemy he hit before. If the attack succeeds, the target takes damage normally and must succeed at a Fortitude saving throw or die. The DC for this save is 10 + 1/2 the imitator's level + the imitator's Intelligence modifier. Whether or not the target succeeds, it cannot be targeted by this ability again (by any imitator) for 24 hours.