Old-School Psionics takes a "what if" approach to psionics, presenting an alternate set of rules to those found in the original core rules.
If you'd like to bring psionics into your game without the need for complicated charts and attack matrices,
Old-School Psionics presents the Mentalist, a new character class dedicated to psionic abilities, which are detailed similarly to spells and broken down into seven levels of power.
Psychic abilities are broken down into four disciplines and dozens of new abilities are presented.
Old-School Psionics also brings back several classic psionic monsters including the Aboleth, the Duergar, the Brain Mole, the Doppleganger and the Intellect Devourer.
Some new monsters are also included such as Men (Astral Wanderer) and the inscrutable Unseen Masters.
Finally, a brief campaign sketch is presented that takes place in the Astral city of Nexus, gateway to the planes, which includes random encounters and sketches of several alternate prime material planes for characters to visit.