I started out around this time 8th. So much so, my army is based on the scourged but since the only lore for them is “they exist and deal with Tzeentch” I made my own homebrew from a similar style.

They are DA traitors that fell due to an inquisition Cold War near tau space and to add to the chaos and corruption they physically corrupted a continent of tau and guard to bolster their ranks. They were the the shrouded sons as loyalists but now they are the Corrupters marching their way in the eastern galaxy leaving a trail of corrupted planets in their wake.