Magic Absorb, Force Shield, 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 Magic Absorb and Force Shield were still present in the 15 September, 1996 build, but it is not possible to obtain the spells through gameplay in that version.
Magic Absorb protected the player from magic damage, but not melee or missile weapons. It was obtained from the Force Shield and Magic Absorb Dungeon.
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.
Kain is protected from the magic spells of these attackers as long as Magic Absorb is active.