Who were 'The Old Ones' mentioned in Star Trek TOS

Question

Who were The Old Ones mentioned in Star Trek, The Original Series. They were mentioned by Ruk in the episode "What Are Little Girls Made Of" and by Korob and Sylvia in "Catspaw."

"What Are Little Girls Made Of?":

Questioned about his origins by Kirk, Ruk remembered that the androids, presumably including himself, had become frustrated by the illogic and inferiority of the Old Ones. In turn, the Old Ones became frightened of their creations, and began turning them off. Their survival at stake, the androids overcame their programming and slew their makers. Once Ruk remembered this, he overcame Korby's programming the same way. No longer able to control Ruk, Korby destroyed him.

_{Memory Alpha: Ruk}

"Catspaw":

Elsewhere, Sylvia and Korob argue; Sylvia likes her new sensations. Wherever these aliens call home, they have nothing like it – and she intends to remain here. Korob reminds her they have a duty to the Old Ones, a fact she considers unimportant in light of her new infatuation.

_{Memory Alpha: Catspaw (episode)}

Answer 1

Probably two different groups

The first group built the androids of Exo III. From "What Are Little Girls Made Of?":

KIRK: Why? Can't your memory banks solve a simple equation like that? What happened to the old ones, Ruk?

RUK: So long ago.

KIRK: Is it possible they built their machines too well, gave them pride and a desire to survive? Machines that wanted logic and order and found that frustrated by the illogical emotional creatures that built them?

RUK: Yes, the old ones. The ones who made us. They grew fearful of us. They began to turn us off.

KIRK: And isn't it Korby who's creating the same danger to you all over again? Unlike you, we humans are full of unpredictable emotions that logic cannot solve.

RUK: Yes. Yes, it had been so long ago, I had forgotten. The old ones here. The ones who made us, yes. Yes, it is still in my memory banks. It became necessary to destroy them. You are inconsistent. You cannot be programmed. You are inferior.

Ruk implies that the Old Ones were destroyed.

By contrast, in "Catspaw" Korob and Sylvia speak of the Old Ones as though they are still alive:

KOROB: We have a duty to the old ones.

SYLVIA: What do they know of sensations? This is a new world.

Since "Catspaw" was broadcast in October 1967 and takes place at Stardate 3018.2, and "What Are Little Girls Made Of" was broadcast in October 1966 and takes place at Stardate 2712.4 , the first episode takes place at a later time, chronologically. If the Old Ones are still alive in that episode, they can hardly be the same group.

Further, Korb and Sylvia are possessed of potent transmutation technology, so far advanced as to seem almost magic. If this is what the Old Ones of that episode provided to them, it seems unlikely that they would have been frightened by mere android consciousness.

So there likely are two groups: one a society of approximately Voyager technology levels that could create sentient AIs of human-like intelligence, the other a species of vastly advanced extra-galactic beings that possessed technology far in advance of the Federation, Borg, or what-have-you.

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That said, there is a link between the two episodes.

Both "What Are Little Girls Made Of?" and "Catspaw" were written by Robert Bloch. As suggested on Memory Alpha, Bloch, as a writer of Lovecraftian horror, would have been familiar with the Great Old Ones of Lovecraft's mythos, which might have inspired him to include the term in the episodes he wrote. Indeed, the Lovecraftian Old Ones could be the same as the entities in "Catspaw." Still, the dissimilarity between the two groups of Old Ones in the episodes written by Bloch is sufficiently great that they are very likely distinct.

Answer 2

Neither group was ever mentioned canonically again, so we can't know. Greg Cox tossed in an explanation of what happened on Exo III in his novel series overarchingly titled "The Q Continuum" but I am unaware of anyone who has addressed the origins of Sylvia and Korob. Do recall from the end of the episode that they weren't even remotely humanoid. In addition, the methods employed by the two explorers on Pyrus VII had little in common with science as understood by the Federation, whereas the androids of Exo III were highly advanced but still understandable. Indeed, a different non-canon novel (Immortal Coil, by Jeffrey Lang) suggested that Dr. Soong learned things on Exo III that went into Data's design.

Although I am unaware of any definitive, canon statement I aver that the two groups were not the same beings, based on these facts, both canon and not. I restate for the purpose of clarity that I regard this as an educated guess, not a truth.