Board Thread:Warhammer 40k General Discussion/@comment-9558536-20130517084538/@comment-4264245-20130520165840

In the time of the Old Ones, it was calm because they were the first sentient and psychic species of the galaxy. Then they decided playing alone with the universe was boring and promoted the apparition of more intelligent species, giving just some nudge there and there and letting evolution do the rest. This led to the apparition of hundreds of species, among which were the Necrontyr and who knows what else. We don't know if those species were able to influence warp, but the ones created during the War in Heaven were, since the C'tan were defenceless against the warp power. Like you said, the fact that we only know of the Eldar and the Krork doesn't mean there were no more (Lexicanum mentions the K'nib and the Rashan). If they had to fight against the zillions of Necrons and the power of the C'tan, they couldn't be just a few, and they couldn't be powerless. Imo, their losses during that extremely long war could have been powerful enough to accumulate enough bloodlust, honour, fear, mercy, ambition and hope to give birth to Khorne, Nurgle and Tzeentch.