The Elder Scrolls: Arena

The Elder Scrolls: Arena is an epic fantasy open world action-adventure RPG developed and published by Bethesda Softworks for MS-DOS in 1994. It is the first game in series. In 2004, a downloadable version of the game was made available free of charge as part of the 10th anniversary of the series. Like its sequels, Arena takes place on the continent of Tamriel, complete with wilderness, dungeons, and a spell creation system that allows players to mix various spell effects.

Story
"The Legend Begins

The imperial battlemage Jagar Tharn betrays the Emperor Uriel Septim by imprisoning him in an alternate dimension, then assuming the Emperor’s identity and place on the throne. A lone prisoner must travel to Tamriel’s most famous and dangerous sites to collect the shattered Staff of Chaos, save the Emperor and free the Empire."