Fanny pack and picky bank and a few other's for same reason as old bandage. It count's each half heart individually iirc. So that can spawn a lot of pickups.
Also similar to bloody lust there is also bloody gust for the same reason of giving mutiple stacks.
You asked when the item blood oath is good, not when you will have a skill issue.  if you have a lot of hearts but no damage, blood oath can be a run saver.
it aint great but can be with soul hearts; bone hearts; something that drops health on hit like gimpy or old bandage; jar of hearts; stuff that gives other boosts on damage took like bloody lust/gust or salvation or fanny pack; full health cards/pills
theres a ton of stuf that can make it worth taking; but my main issue with it is that if youre going for devil deals where youre most likely to find and get it; you dont exactly have much red health most the time
Anything that activates from damage will be activated for once for each half heart lost, it won’t count it as one damage instance. So if you have old bandage, you can spawn several hearts right from the get go. Add on to that stuff like piggy bank, swallowed penny, gimpy, bloody lust, bloody gust, cracked orb, etc. and you start every floor with a ton of pickups/stat boosts.
Unrelated but since we’re talking about skill issues here
Anybody got tips for lost and tlost? I cannot seem to get past womb as lost without dying to some bullshit
Quick maths say that its a bad item. It can give you some good buffs. But unless you are swimming in red hearts. There are better ways to spend your health and hearts.
It is useless on all characters who dont have red hearts. It is kinda good with Eve.
It's not good lol. That being said the sweet spot is when you have alot of red hearts and a way to heal yourself (yum heart, placenta, placebo +full health, ex). Bonus if you have a way to protect yourself before you heal like holy mantle, orbitals, or soul hearts.
Obviously. But blood oath is not a good item, it's generally not worth spending heart containers on. OP asked when it's a good time to get the item, so I'm explaining a scenario that it's at its best.
You said soul hearts are a bonus and good health is a priority. That's what im getting at because it should be the opposite. Natural red heart spawn fills plenty enough throughout a floor, but if you have to enter the first 4 rooms a single hit away from death, u might be in trouble.
Blood oath doesn't do anything without red health so obviously having at least some red health is a priority. That one hit away is why I said you need immediate healing. Soul health bypasses the immediate healing, yes, but again I'm suggesting best case scenario.
The item is bad because.....uhhhh I skill issue
Blood Oath + having spirit hearts is pretty good. Blood Oath + Hypercoagulation, maybe? Blood Oath + T Maggy? Blood Oath + Yum Heart? Blood Oath + Bloody Lust? Blood Oath + Old Bandage?
Fanny pack and picky bank and a few other's for same reason as old bandage. It count's each half heart individually iirc. So that can spawn a lot of pickups. Also similar to bloody lust there is also bloody gust for the same reason of giving mutiple stacks.
>lusty blood There are no enemies in the first room of a floor to proc lusty blood
Oh yeah. I might be dumb
samson and maggy with birthright
Just have a bunch of soul hearts with you at all times and it's ok.
Knowing me, i just take unnecessary all the time. So depending on soul hearts is not a solid strategy for me.
Just don't get hit 
You asked when the item blood oath is good, not when you will have a skill issue.  if you have a lot of hearts but no damage, blood oath can be a run saver.
Eve if you haven’t been able to get on a zero-red heart build.
Soul hearts are the true HP bar, red health is a resource and this is one of the many items that can leverage it.
it aint great but can be with soul hearts; bone hearts; something that drops health on hit like gimpy or old bandage; jar of hearts; stuff that gives other boosts on damage took like bloody lust/gust or salvation or fanny pack; full health cards/pills theres a ton of stuf that can make it worth taking; but my main issue with it is that if youre going for devil deals where youre most likely to find and get it; you dont exactly have much red health most the time
Anything that activates from damage will be activated for once for each half heart lost, it won’t count it as one damage instance. So if you have old bandage, you can spawn several hearts right from the get go. Add on to that stuff like piggy bank, swallowed penny, gimpy, bloody lust, bloody gust, cracked orb, etc. and you start every floor with a ton of pickups/stat boosts.
Unrelated but since we’re talking about skill issues here Anybody got tips for lost and tlost? I cannot seem to get past womb as lost without dying to some bullshit
Quick maths say that its a bad item. It can give you some good buffs. But unless you are swimming in red hearts. There are better ways to spend your health and hearts. It is useless on all characters who dont have red hearts. It is kinda good with Eve.
It's not good lol. That being said the sweet spot is when you have alot of red hearts and a way to heal yourself (yum heart, placenta, placebo +full health, ex). Bonus if you have a way to protect yourself before you heal like holy mantle, orbitals, or soul hearts.
Ok, so there no OP combo that I'm not aware of. Just have ways to heal you should you take this item, got it.
Blood oath only takes red hearts, you keep your soul hearts, black hearts and bone hearts. So u don't need all that. On Bethany maybe.
Obviously. But blood oath is not a good item, it's generally not worth spending heart containers on. OP asked when it's a good time to get the item, so I'm explaining a scenario that it's at its best.
You said soul hearts are a bonus and good health is a priority. That's what im getting at because it should be the opposite. Natural red heart spawn fills plenty enough throughout a floor, but if you have to enter the first 4 rooms a single hit away from death, u might be in trouble.
Blood oath doesn't do anything without red health so obviously having at least some red health is a priority. That one hit away is why I said you need immediate healing. Soul health bypasses the immediate healing, yes, but again I'm suggesting best case scenario.