What's the most 90s way you can market your retro-styled prequel to a 90s mech shooter? Other than an Acclaim-style stunt where you offer people £500 to tattoo their baby's face with the game logo, I'd say perhaps releasing a Quake mod. So here's Episode Enyo, a prequel to upcoming "biopunk" hack 'n' slasher Slave Zero X, now available as a Bethesda-approved free add-on inside Quake.