I love hymn / tanglewire / etc but those cards can be really rough if your cube sessions are under a very limited amount of time or you don't get to play often. Generating non-games is harder to get over if you have few to start off with.
Also remember that you want to make these cards impactful not devastating. Black does need cards that generate card advantage without dealing with life but like don't force people to play with decks filled mainly with 3-4-5cc sorcery speed cards and try to include more card advantage and selection across all colours for recovery. Midranged decks can lose the half of their hand that meant business and feel really stranded by cards like these.
Also remember that you want to make these cards impactful not devastating. Black does need cards that generate card advantage without dealing with life but like don't force people to play with decks filled mainly with 3-4-5cc sorcery speed cards and try to include more card advantage and selection across all colours for recovery. Midranged decks can lose the half of their hand that meant business and feel really stranded by cards like these.