For reasons known only to themselves, during the 1990s the Games Workshop design team decided that both their flagship fantasy battle game and their rising space opera spin0ff, Warhammer 40,000, needed to use the same sort of card-based magic system. For the 40k version, the term "magic" was discarded in favor of "psionics" or "psykers."
It was not popular. During the entire time Warhammer 40k 2nd Edition was current, I only used the psyker rules twice, both against the same Eldar player.
It really came down to efficiency. The psyker rules added a lot of complexity to the game with little to show for it. In a medieval fantasy environment, throwing fireballs is a big deal; in a game with tanks, rocket launchers, and flamethrowers, a fireball is just another hand grenade.
I should add that in both 40k games where psykers were used, they were ineffective. Again, D&D style magic doesn't make much of an impression on people throwing miniature black holes around the battlefield.
[The opposite was true in the 5th edition of Warhammer Fantasy Battles, where magic came to dominate the game - much to its detriment.]
So why am I taking a second look after all of these years?
The answer is that there are technically two sets of psyker rules for 40k 2nd edition. The deluxe set with all the cards does not interest me, but in the core rule book, there is a simplified system that would add minimal complexity but allow psyker characters to assume a battlefield role. That's why I'm interested.
You see, as the years have passed, I've gotten interested in exploring more aspects of the game. One area that I've never even touched on is using the basic psyker rules. I don't think these will make much of an impact on game play, but I like the idea of it adding some color to the campaigns we run.
It also presents the opportunity to use previously sidelined unit and character choices. Many of these had aspects beyond psionic use, but since they were priced with psyker abilities in mind, they've been idle. This provides a chance to expand my battlefield options a bit.
Yes, it also opens some space to collect a few additional models, but that's not much of an issue. I generally don't use GW models and I've got so much stuff kicking around the collection that I don't think it will amount to much. The most likely impact is that I will get out some of the unfinished stuff and repurpose it as psykers.
The longer one collects, the larger that 'reserve' becomes. Mine is not as big as 25 years of collecting would indicate because when we moved into our present house, I sold off a lot of the excess. Indeed, I've continued to do that periodically as part of my drive to reduce clutter.
In any event, I think it offers some interesting possibilities and look forward to seeing what happens.