Would have to adapt a new system of new types of hearts, so here we go:
The Relic
generates soul hearts, can be used to buy cheaper angelic babies.
Cost: 150 Red Hearts
Cost: 100 Soul Hearts
Cost: 150 Black Hearts
generates black hearts, can be used to buy cheaper demon babies.
Cost: 150 Red Hearts
Cost: 150 Soul Hearts
Cost: 100 Black Hearts
Note: The system of hearts that fall from the sky can be by type of floor(level), in addition, all babies that do not enter the specific characteristics of hearts, do not have a reduced price compared to other types of hearts.