From the back of the box (original Dro Soft Spanish release):
Acción sin tregua en la primera aventura gráfica con sistema de animación tridimensional. La búsqueda del pergamino te va a llevar a través de múltiples pantallas, a enfrentarte con cientos de enemigos diferentes. Pero mientras conserves to Brio. Ia victoria sólo puede ser tuya.
From the inlay (Mastertronic English re-release):
In the eleventh Century a parchment was left on the Earth. On it was inscribed a diabolical magic spell which could unchain the forces of evil and guarantee Satan's supremacy as the Price of Darkness. Rodrigo Diaz, 'El Cid', a gallant knight, was aware of the terrible threat and vowed to find the spell and guard it until it could be neutralised by two men of prayer. [...]
[T]he parchment must be seized from evil forces which are currently guarding it. They also hold Donna Jimena, our hero's wife. She alone is a source of inspiration to him and only she can restore strength to his weary muscles.
The original Spanish version was written by Manuel Orcera Valero and Francis Moragrega and released by Dro Soft on the Spectrum, Amstrad and MSX. It was later translated into English and re-released by Mastertronic with the Amstrad and Spectrum versions on a single cassette.
The game is an action adventure viewed from an isometric viewpoint. The player must fight his way through hordes of enemies to retrieve the parchment, then fight his way back to destroy it before Satan takes over the world!