Arachnokillers were biotically created creatures formed by the Columi brothers, Craitheus and Marvid Qreph. They were spider-like animals that could be kept inside glass tubes. They were designed to explode under stress and could be used in assassination attempts.
In 45 ABY, the Qrephs gave three arachnokillers to their agent, Dena Yus for use in an assassination attempt on Han Solo and Lando Calrissian at the Blue Star casino. However, Yus' loyalty to the Qrephs wavered during the mission, and she failed to deploy the creatures. When a firefight broke out at the casino when the Qrephs' agent, Mirta Gev attempted to take Solo into custody, the arachnokillers were released. When a Gran patron slammed a glass onto one of the arachnids, it exploded in a bright white explosion, incinerating the Gran. Calrissian fired a blaster at the remaining arachnokillers, causing the creatures to explode and destroy the casino, allowing Gev to take Solo captive.