What device is used to resolve combat outcomes in Quest of the Ancients?

Context: Quest of the Ancients is an independent role-playing game published in the late 1980s by Unicorn Game Publications. It is mainly a Dungeons & Dragons clone, in that it was character class- and level-based, used a Dungeon & Dragons style Vancian Magic system, and used a skill system similar to the Advanced Dungeons & Dragons thief skill system. Most notably, it used a thirty sided die for combat resolution. Written by Vince Garcia of Fresno, California, the game system implements a large number of character classes.

Answer: A thirty sided die (or d30) is used for combat resolution.