Psionics involve the use of the mind to alter or command reality, typically through some understanding of a deeper truth about the universe or command over a fundamental law of reality.
It’s pretty cool, but I have trouble thinking of media where it takes a prominent role. The few examples that come to mind are:
Star Wars - The Force Mass Effect - Biotics/Element Zero technology Stellaris - Spiritualist Ethos Warhammer 40k - Psykers/Orks
What are some other examples of psionics in Sci-Fi?
Starcraft had the Ghosts.
That may be based on something in Warhammer 40k, which you already mentioned, as I understand that some elements of the game were based on Warhammer 40k. I’m not really super-familiar with the lore of the two enough to know, myself.