Realms of Chaos

Realms of Chaos is one of the many action games 3D Realms made back in the days they called themselves Apogee.

Endrick, the warrior, and Elandra, the sorceress, have to travel through 26 levels, split into 3 'episodes' to find the source of what's corrupting the land of Mysteria. Endrick uses his sword fight enemies in close combat, and Elandra uses a supply of gems to blast them with fireballs from a distance.

You can switch between characters at any time, but they both share their own health bars, and if one dies, you'll still need to restart the level.