The Gress'sril was a 23rd century Gorn starship, a MA12 class VI cruiser. In the 2260s, this vessel was under the command of S'slee, and was the instrument of the devastating Gorn attack on the Federation outpost at planet Cestus III, the Cestus III Massacre. (TOS episode & Star Trek 2 novelization: Arena; ST modules: Demand of Honor, Star Trek IV Sourcebook Update)