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Triad Stone is a full motion video game developed by Data East and presumably finished in 1985. It is presumed to have been designed for LaserDisc hardware similar to Dragon's Lair, though in its original 1985 form (named "Cashing Stone" (キャッシングストーン)), the game does not appear to have been released.
In 1994 the game was ported by Sega to the Mega LD platform in both Japan and North America, being the only Mega LD game to be published by Sega. The publishing rights were later picked up by Media Entertainment who released Sega Saturn and 3DO ports as Strahl: Himerareshi Nanatsu no Hikari (シュトラール 秘められし七つの光). The Saturn release was not released outside of Japan, though the 3DO version of the game was localised for a US audience simply as Strahl.