With Bone Hearts, Red Hearts contained within the Bone Hearts will be taken before regular Red Heart damage.
If Isaac only has half a Red Heart left / has no Red Hearts left, Soul and Black Heart damage will be taken, and Bone Hearts can be destroyed.
Notes
This is useful for getting into Boss Challenge Rooms while maintaining Soul/Black Hearts.
No longer works as Boss Challenge Rooms now require one heart in total.
Red Heart damage taken via the trinket affects Devil Room/Angel Room chances normally.
This can be used to voluntarily decrease the Angel / Devil room chance if it has already been accessed in favor of increased chance next floor.
If Isaac has at least one Rotten Heart he does not lose deal chance from taking any red heart damage, despite rotten hearts not being taken first.
This means having just a single rotten heart can be a great strategy for removing the majority of the downside of this trinket.
Although Gold Hearts are in front of the HP bar, they will shatter when red heart damage is taken through the trinket.
This trinket is useful when playing as The Forgotten, as it will preserve his Bone Hearts (and Devil/Angel Room chance) until all of his Bone Hearts are empty.
This trinket does nothing while controlling The Soul.
Red Heart damage will be taken before 
Soul Heart, 
Black Heart, and 
Rotten Heart damage.
Bone Hearts, Red Hearts contained within the Bone Hearts will be taken before regular Red Heart damage.
only has half a Red Heart left / 
Boss Challenge Rooms while maintaining Soul/Black Hearts.
Devil Room/
Angel Room chances normally.
Gold Hearts are in front of the HP bar, they will shatter when red heart damage is taken through the trinket.
The Forgotten, as it will preserve his Bone Hearts (and Devil/Angel Room chance) until all of his Bone Hearts are empty.
The Soul.
Golden Trinket / 
Mom's Box : No effect.
Eve Unlocks 
Ultra Greedier Unlocks 
The Binding of Isaac: Rebirth
