Force Shield, Magic Absorb, and a more limited version of Repel were three separate spells in early versions of Blood Omen, such as the build from 12 July, 1996. The graphics for Force Shield and Magic Absorb were still present in the 15 September, 1996 build, but it is not possible to obtain the spells through gameplay in that version.
Force Shield protected the player from melee and similar impact-based damage, but not magic damage or missile weapons. It was obtained from the Force Shield and Magic Absorb Dungeon, and was absolutely required for access to large areas of the game (in particular, Malek's bastion), as it was the only way to avoid instant death from whirling mechanical blades in that version of Blood Omen.
By the time the game was ready for release, all three spells had been merged together into a comprehensive spell which protects against all types of damage. That spell was given the existing Repel name and artwork.
Video footage of both deleted spells can be found in the Force Shield and Magic Absorb Dungeon article.