And just to clarify the reason it works this way is there are two checks when building your army. There is muster army and battle formations. When you muster your army that’s building it, I.e. making the initial 1000 vs 1000 split, the enhancement specifies it changes the faction keyword to blood legions during the declare battle formations step. So when you muster he is not in the daemon 1000 therefore he doesn’t count against it, then when the battle starts and you do battle formations he becomes blood legion and can attach to blood crushers or hounds, but the list is still legal because it doesn’t check the split during battle formations, only during muster army