Originally Posted by
TsumiBand
Ghastly Conscription makes me think of the old Haunting Echoes "win condition" where simply exiling the bulk of your opponent's deck was enough to force a scoop. Casting this instead of Echoes would be less crippling but would give the same deck the ability to untap and just win the next turn.
None of that is Legacy notable, of course - Mono-Black Control isn't a thing, especially not the Odyssey Block deck I'm fondly remembering, but... that is what I thought of when I saw that thing. A large Black spell a control deck casts in order to end the game (either on a technicality, or for realsies).