Hunh? I have every one of the 2nd edition books right next to me, about 2 inches away....and yes, the monsters and NPCs do all have psionic talents, even if they're just wild talents (as they called them in AD&D 2nd ed).
But that is verifiably false.
While every PC must have a wild talent if not a full psionicist, per page 19 of the
Dark Sun Rule Book, "Every player character has at least one psionic talent,
as do many of the non-player characters and monster." In other words, not all.
The first Dark Sun Monstrous Compendium states under the description for Psionics, " . . . A large percentage of Athasian creatures have psionic powers." So . . . no all.
In the
Revised Dark Sun Campaign Setting, this was ratcheted down significantly. Page 18 of
Way of the Psionicist, "Every character and monster had a base chance of 1% of being a wild talent (10% for Dark Sun NPCs and Monsters).
Let's find some. Excluding nearly all the animal and non-intelligent creatures that had no psionic power (
but some animal intelligent creatures still did! like the Agony Beetle, Cistern Fiend, and Kes'trekel), all monsters did not have psionic power, even wild talents. Digging through both Monstrous Compendiums, the following psionic monsters have greater than animal intelligence and have
Nil for Psionic Summary, i.e. the creature's innate psionic ability.
Bog Wader
Greater Elementals, (Air, Earth, Fire, Water)
Lesser Elementals, (Same)
Plains Giant
Desert Giant
Dhaot
Dune Reaper Drone
Elemental Beast, (Air, Earth, Fire, Water)
Paraelemental Beast, (Magma, Rain, Silt, Sun)
Fael
Shadow Giant
Sand Bride
Sand Mother
So-Ut
Spirit of the Land
Tohr-Kreen (Mantis Noble) 10% chance
Magma Golem
Salt Golem
Ash Golem
Chitin Golem
Rock Golem
Obsidian Golem
Sand Golem
Wood Golem
Pakubrazi
Raaig
Ruvoka
Slig
Ssurran
Tari, Tari warrior, and Tari Chieftan
Tohr-Kreen (J'hol) (about 50% have wild talents)
Torh-Kreen (T'keech) (about 50% have wild talents)
Torh-Kreen (Tondi) (about 50% have wild talents)
Trin (and naturally resistent to psionics)
T'liz
Athasian Wraiths
Thinking Zombies (unless previously a psionicist)
The list would probably double if I included every animal intelligent creature with Nil for psionic powers.
Really, not everything had psionics in Dark Sun. But all PCs did.