I was recently reading the back of the 3rd edition rulebook, and i found out that i could include certain aspects into my space marine army. One of these units, was an Elite unit choice, the Imperial Assassin. Reading up, i found out i could include him in any space marine army, and he was looking as a valuble option. But i also heard that i can only have it in a witch hunter or Dameon Hunter army, and i already made up my mind that my army would be just a standard space rine army, and that if i do decide to choose an assassin, i have to use the 110 point on in the Daemon hunter codex? What do i do???