This is the Fantasy Warriors Companion (1992), a rules expansion for the full Fantasy Warriors game. There are two main modules, one for the Necromancer, which provides specific rules for playing an Undead army, one for Mercenaries, which allows a greater variety of unit to take the field. The remaining space is devoted to army lists.

I mostly bought this for the illustrations, primarily by Mark Gibbons, with some pieces by Ian Symonds and frickin’ Tony Ackland. They’re cool because they’re all essentially drawn from the sculpts (or were concept drawings for the sculpts, I suppose; impossible to know) and that’s cool to see.