Question: ck2 when do seljuks arrive?
Answer: In the year 965 or soon after, Seljuk will appear in the court of a landed duke+ ruler whose culture is Turkish, Cuman, Uyghur, or Karluk. (If no such rulers exist, Seljuk cannot spawn.) If the game rule "Turkic Conquerors" is set to "Random", Seljuk may appear as soon as 809.