If you check the "Restrictions" section in the Blood Host (in the grey bit just below where it has Core, Auxiliary & Command.
"For each Core choice you must include between 1 and 8 auxiliary choices..."
Before all that in the white part it says "Unlike the Detachments shown in the Warhammer 40,000: The Rules, it has a Force Organisation Char whose slots are a combination of specific Formations and Army List Entries."
So yeah sorry, the "War Engine" is just a Auxiliary Choice and counts as just a "Army List Entry". Same goes for Flayed Ones, Deathmarks and Star-God from Necrons.
Otherwise I think I would endlessly be taking Nightbringer in pretty much every army, as for 240pts he is a BEAST!
Last edited by mayegelt; 03-28-15 at 07:26 PM.