While editing the third Dungeons & Dragons supplement, Eldrich Wizardry, Tim Kask developed D&D’s first rules for psionics. He loved psionic combat and threw his enthusiasm into the task.

His rules answered D&D’s biggest critics. First, they stood separate from unrealistic notions of class and level. Second, they adopted a point system similar to the spell points touted by critics of Vancian casting.

Kask balanced and tested psionics to perfection. But when Eldrich Wizardry and its new psionics rules reached fans, some liked the topic, but few liked the rules.

Few players cared to learn the intricacies of psionic combat with all its tables and charts. Some players liked adding the extra powers onto their characters, but hardly any DMs allowed psionic characters in their game. The new rules mostly ignored D&D’s system of class and levels. They unbalanced play.

Tim Kask balanced psionics for a setting where intellect devourers, brain moles, cerebral parasites and other creatures sensed psionic users and sought them as prey. He loved psionics and imagined a game-world that fostered mental duels against psychic creatures.

In practice, nobody played D&D Tim’s way.

Psionics suffered from more than imbalance. Psionics grafted an complicated new game onto D&D. Virtually nothing in the new rules resembled rules already in D&D. By creating rules that answered D&D’s critics, Kask created rules that failed to match the rest of the game.

Role-playing games without character classes and with spell points can work brilliantly in a game like Runequest (1978), but the incompatible rules fared badly in D&D.

Perhaps the failure of psionics taught Gary Gygax some things.

In the July 1978 issue of The Dragon, Gygax would defend D&D’s character classes from critics. “If characters are not kept distinct, they will soon merge into one super-character. Not only would this destroy the variety of the game, but it would also kill the game, for the super-character would soon have nothing left to challenge him or her, and the players would grow bored and move on to something which was fun.”

Gygax also defended Vancian casting against point-based systems. “Spell points add nothing to D&D except more complication, more record keeping, more wasted time, and a precept which is totally foreign to the rest of the game.”

Now, game designer see value in keeping game rules concise and applying a simple rules broadly. Fifth-edition designer Mike Mearls wrote, “You’re more likely to introduce elegance to a game by removing something than by adding it.” But in 1975, folks were still figuring out RPG design. So designers like Kask felt free to graft a psionics game onto D&D. Whenever Kask talks psionics now, he explains that he would design them differently.

Even as Eldrich Wizardry went to press, I suspect Gygax understood some points he would argue later. So why did Gygax open D&D to a psionics system that ignored classes and that used points? Because during the development of Eldrich Wizardry, Gygax still held to his a long habit of collaboration. If a collaborator like Tim Kask felt passion for some addition to the game, Gygax opened the way. Many of these “official” rules never entered Gary’s Greyhawk game. Still, he welcomed other dungeon masters to pick and choose, to shape their own games. (Over time, Gygax would become more protective of D&D’s rules. For much more on his evolving attitudes, see Basic and Advanced—Dungeon & Dragons goes two directions.)

Psionics became unpopular because it added 70s parapsychology and an entirely different sub-game onto D&D. The concept only lasted because the notion of psychic powers resonated with players.

In the years to come, designers found ways to make psionics at home in D&D. They would integrate psychic powers into settings like Dark Sun, and they would express psionics using D&D’s core rules. For example, when David “Zeb” Cook updated psionics for 2nd edition, he created a mental version of THAC0. Potential psionic rules for 5th edition use character classes and even revive the name of Steve Marsh’s Mystic class.

Gary Gygax experimented with psionic characters to offer players a defense against the terrible power of mind flayers. Eventually, his original justification for psionics moved from the real world into the game world. In 4th edition lore, psionics manifested in the prime material plane to help its inhabitants battle intruders from the Far Realm—intruders like mind flayers.