Still hasn't been cleared up but the engrams may drop from the raid if you have the raid shell. Reason I say hasn't been cleared up is because there's bright and illuminated engrams. Each belonging to a different season. They stated the ghost shell would drop season 1s in the TWAB, but then in the forums they said it would be season 2s. So I don't know, and I haven't seen head or tales of what it does do. So I may have wasted my time typing this, and you may end up wasting your time grinding. Unless I am fortunate enough to have met someone who already knows the answer, save me from my torment.