Originally Posted by primarch-angron
In the lizardmen codex it says that the Old Ones came from a different planet and that they brought up the races of Men, Elves and Dwarfs. I have heard it said that the they are a link between the 40k universe and this one. What do you think? If you think that it is what race do you think they where? and please which ever one you choose can you tell me Why.
The Old Ones have appeared in GWs histories of both the 40k & Fantasy universes since their inception in the mid 80s.
If you look around you can find odd mentions here and ther of the Old Ones as a semi mythical master race in both 40k and WFB, remember that for some time both universe were linked and a lot of fluff crossed over, the Old Ones being one of the few bits of lore that still exists more in less in the same form in both universes.
From a WFB angle, one of the best indepth pieces of writing about the Old Ones is in the 1st edition Warhammer Fantasy Roleplay book, where they were called 'Old Slann'.
(the Lizardman army as it's known now has evolved significantly since the late 80s. First the Old Slann were the god-like Old Ones, then the general 'slann' race came to be an army (& blood bowl team!) withlizardmen and troglodyte unit choices, eventually lizardmen became the ainstay of the army with the near extinct slann becoming the leaders)
The 'Old Slann'/Old Ones introduced much life to the warhammer world and gnentically/magically created or manipulated the races of Elves, Dwarves, Humans and Halflings (and Ogre and more).
It was the collapse of the Old Ones' great gates that allowed Chaos into the world.
In 40k the Old Ones influence is less well documented but little mentions pop up in Eldar lore, the history of the C'tan and the Necrontyr, and elsewhere. I think they're mentioned or hinted at in the novel Legion
in the sections about the cabal.
The sudden appearance of/rapid evolution of the Tau has been linked to the Old Ones, especially as parallels can be drawn between the Tau resistance to chaos, and the same in the WFB Halflings (also immune to chaos), one of the Old Ones last creations in that universe.
So, to answer your question, they weren't a 40k race that stumbled upon the Warhammer world, rather they are something far more vague and interesting.