Mysterian

Mysterian, designed by Wally Welch for Bally, carries a backglass copyright date of 1982, though it never reached production — only about one unit is known to exist, with coin mechanisms suggesting it was placed at a test location before Bally abandoned the game.

The surviving machine is packed with ambitious features for the era: four flippers, a pop bumper, two slingshots, twelve standup targets, six star rollovers, two rollunders, two horseshoe lanes, two bonus ladders, a three-bank of drop targets, a kick-out hole, and two-ball multiball. It even carries two separate "Squawk & Talk" sound boards — one for game sounds and speech callouts (including test-mode snippets borrowed from Eight Ball Deluxe, Fathom, and Medusa), and a second, dedicated to playing an actual synthesized background song rather than looped sound effects, a rarity for Bally machines of the day.

With its Fantasy theme and elaborate hidden engineering — including a ball-lock mechanism built into the left-side playfield loop — Mysterian stands as one of the more technically ambitious games Bally never put into production, known today through a single surviving example rather than any commercial run.