Originally Posted by
Callistarius
From memory, the pain aspect in the form of the Pain Glove was introduced in Ian Watson's novel Space Marine back in 1993. This came out around the time 2nd ed was starting up and I'm not sure that there really was much fluff for the Imperial Fists before that.
If you can, get this novel. It is awesome, unlike the half-baked pretty bad re-hash Sons of Dorn. The way the marine aspirants are characterised is really good, especially the conflicted aspect of the inter-relationship. It kept consistant with old fluff - after the astartes encountered Chaos, they were mindwiped. None of this "everyone in the Imperium knows about the Horus Heresy" stuff - only the Inquisition, High Lords of Terra and Astartes Chapter Masters have the "need-to-know".