Probe killers were tiny six legged assassin droids that could be carried inside the small pits on the head of the larger assassin probes, where they lay dormant until the assassin probe activated them. They were similar in appearance to their larger companions, but only a small fraction of their size. Circa 21 BBY, assassin probes and probe killers were used on the Coronet in an attempt to assassinate Duchess Satine Kryze. Most of the droids were destroyed in the initial attempt, but Obi-Wan Kenobi found a survivor, which he used to identify the traitor aboard the ship.