Bloodborn - All new infernal class with 2 Subclasses

Also have a custom spell list comming.

Having it as a 1 per s/rest is not even worth including that mechanic properly.

Hmm I do see your points, some how though I would like to try and give the class the feel that overpowering yourself does come at an imminent cost and danger. I like the idea of a limited resource like the hit die but feel it takes that danger away from the midst of combat and you'll just be relying on heal spells at rests instead of using you hit dice to heal.

I'm not sure how to really balance it out without stripping the ability out of lower levels, especially as it the focal ability of the class. Would you think that maybe something like a clause that cannot recieve heals in the midst of combat?

Oh also the spell points wouldnt be able to be used for clerical spells as it would just be powering bloodborn spells which none would be heals.

Maybe have it reduce your hit point maximum instead of just flat hp? That can get super scary and limits heals a lot?
Unsure with restoration spells bypassing that, maybe have it that only resets on a long/short ignoring restoration spells entirely?
Hard to ensure balance, as that could decapitate the class as a whole, too.

That actually sounds really good. Is a nice way around it. Also considered exhaustion after going through the lycan barb, but I think this fits better.

Okay then, now that I'm home I can actually reply properly.
Apologies in advance, there will be some comments here that may come across rude, the intent behind them is to drive home a point, plus I'm tired and rushing because I gotta wake up early tomorrow, heh
Also, I may actually dig hard here and fail to provide you alternative ideas on things, but I do plan on doing so at some point. I just want to get some points out front hard for this.


Blood Well:

Now, this is always dangerous. A one off ability, with extra uses later (9th lvl is -VERY- late for the extra). You'll never use this in a really dire situation to bring yourself low, so you need to provide an incentive for that. Because as a player, you'll not want to risk being so low on HP (especially without healers around), you'll only drop just enough to get a handful of spells. As a 1st level mechanic it's nice, but it should have ever increasing viability, and the ratio needs to be high enough not to be exploited.

at 3 hp = 1 sp, you've also got the following HP for the class (always base your calculations off max for most potential available)

lvl 1 = 16 hp max (hill dwarf w/ +5 con)
lvl 4 = 72 hp max / 58 avg (add Toughness feat)
lvl 8 = 144 hp max / 114 avg
lvl 12 = 216 hp max / 170 avg
lvl 16 = 288 hp max / 226 avg
lvl 20 = 360 hp max / 282 avg

Add another 20 hp from an Ioun stone, and more for other items that may increase flat con above 20.

Can you see a problem with spell point transfer rates yet? I can effectively, best case scenario I can drop my max hp by 100 and gain 33 SP. That's about a third of my health from my average, less from my max. at lvl 8, that's 2/3 my max HP, but that's still more than the total SP I even have! The negative is not actually going to have a single horrible effect at all. At high levels, I couldn't give a rats ass, I want that 50 sp, take the 150 hp and I'll rely on spells to cover my ass. I can drop my hp from 282 to 82, and gain around 67 SP from that. And just be like, sure, I'll short rest now and then heal up and I'm freaking good to go. I would never select an option for health that would ensure my character dies because of it. Nor would my character do that, practically. It may come up, but it won't come up enough to warrant a conversion ratio of such power.

Now the issue comes to being, what is the right ratio? If you do 5 hp - 1 sp, that's 10 sp for 50 hp? Is that worth it? In some circumstances, maybe.. but even then, the best I can get is 5x lvl 1 spells, or a single lvl 7. Will you ever truly be at risk? Nope, not even, you've got HP out the ass, and you will find items to supplement your durability as well (imagine this guy with armor of invulnerability, no dmg taken for 1 min? Time to drain myself over and over to 1 hp and still win!).

This is the problem with using HP as a resource, there is simply no fixed power ratio to transfer off. You have to base it off the HIGHER probably outcome, and be damned to the lowest. Those characters that don't get toughness, go dwarf or get to pump their con high enough, that's where it can be come painful for them to use. And I don't mean that in a fun way. If you roll HP, even as the dwarf above, and roll nothing but 1's, you're almost never going to use this ability for big effects, instead just siphoning little at a time to stay all good. Then you'll siphon it down before a short rest to power right back up and enjoy healing benefits from there.

Anyway, enough on that.

Life Tap:

Awesome, now lets look at broken combinations. 
What is classified as a minion? Anything you summon? How about from items, spells, or RP stuff with creatures under your control? What about that hireling human craftsman you got to maintain your castles gate? What classifies as under control, if a cleric summons a Balor and tells it 'obey the bloodborn', is it considered under my control? Can I drain over 150 hp in one go then?
How about something that lets you summon something every single day for a portable healing machine? Such as a large elemental.
What about something that has resistance to damage? Or immunity? Does this deal damage, can it be negated, reduced, ignored, or even increased? 
What's 50% of 1 hp? Just curious.


Bloodmage:


Bonus Cantrips: 

Why minor illusion? what the, huh? Where's the theme there? Blood, demons, summoning, souls.. illusions? Huh?

Born of Blood:
.. interesting. I actually like this, but I would consider giving it more control of itself since it's not just a generic animal, but a literal fucking demon. Have it function on it's own initiative count and make it's own attacks/actions. 
I would also consider not allowing it to be done as a 1 action summon replacement, keep it to the track of the summoning spells that exist, they take time to prepare. Also, the 10 sorc point cost is higher than the sorc points you have at 3rd level, that mechanic is pointless as a starting ability. Plus, 10 sorc points is a lvl 7 spell, never using that except to keep twinned soul active, which will never have to happen due to below comments.

Twined Soul:
Is there a duration for this? Does it take concentration, or have a range? What if I put my demon in a safe and secure area and give it healing potions. I command it to drink them as it takes damage, and I spend the rest of the game with permanent resistance to all damage.
Why would I EVER end this?

Soul Shift:
Nope, not ever using this. I have resistance to damage permanently here, not risking it. And my minion won't ever be in range for this, it's sitting in its nice safe area with permanent healing available. It'll have friends over and be watching magic videos of pirates of the inner sea, with Jonny Derp starring in them. 

On a wording thing, 'can use reaction to trade place with your minion as long as they are within 60 ft', the 'they' should be 'it'
10 spell points is a lvl 7 spell. Never using that to use this twice.


Blood of the Demon:
Great theme, flavor and idea.
Never using it, I have permanent resistance.
As a 20th lvl capstone, this is actually quite bad as well. You'll never use it on a Quasit or Dretch, only a shadow demon. Which actually gives you worse abilities than just keeping the shadow demon and keeping it to use as a resistance wall with its own healing.



Tained:

Blood Taint:
Having it scale up in damage dice size I think isn't worth having. Refer to the Hellish Rebuke ability for scaling aspect. I would also suggest basing it more off that, and if restricting it to just melee I think a damage buff is more than justifiable at that point. As it is, it does cantrip sizes damage, once per short rest. It's worst than the Tiefling gets naturally As a 3rd level ability, have it just straight up to 2d8 damage.

It needs to state what happens on a successful or failed save, it just says make a save or take it. See the Hellish Rebuke spell for saving throw terminology, it'll help to ingrain that into anything you write that involves a saving throw to provide clarity.

The taint that lingers, does it require concentration? If not, state that in brackets please

The subsequent enemies that harm you part is too vague. What if that enemy harms you from a ranged weapon or spell, does it effect them too? What do you consider harm, does casting Dominate Person on you and tricking you into jumping off an illusory bridge count as harm? If it functions the same as the trigger, list it as 'This effect remains active for 1 minute (no concentration required?), any creature that deals damage from a melee attack also suffers this, as above.' or some such.

Rather than say 'if you expend', rephrase it to 'When you use this ability, you can reduce your hit point maximum by 5 to increase the damage dealt by an extra XdX necrotic damage'. Phrase it similar to the At Higher Levels wording for spells, for continuity and simplicity.


Lifes Blood:
You've listed it as 'current hit points total by current hit points', you need to clarify this as temporary hit points specifically, though you refer to this later, you don't actually say you gain temporary hit points at all, just that you get current with current. 
Change it from 'subject to death saves' to 'and are dying' - that's the term for this edition.
This ability will not see use in anything but the MOST dire situations, and even then you're likely to find that it'll never have a detrimental effect, it'll never be used to bring you to 0, because if your hit point maximum is reduced to 0, you die. Outright. No questions. No saves. Dead. Utterly. 


Infernal Pursuit:
A creature hits you in melee from Tainted Blood, you can now teleport to it? Wait, what? It's right beside you? I won't need to teleport, I can just hit it. Does teleporting use my movement, does it use an action/bonus action/reaction, or nothing? Can I move -AND- teleport (like shadow monk)? Where to land, do I have to adjacent to it? What if I use a polearm and wanna use my reach, am I now stuck B2B next to it?
Also, why teleport when it's beside me?



Demonic Fury:
'expend up to half my hp maximum' ?? Expend? -Reduce- i the word here I think you want. 
Wait, you're saying 10 hp = 1 weapon attack? So, I shouldn't use this at all if I need to attack twice? 
The 10 hp is equiv to a lvl 2 spell.. that'd do more damage than my melee attack? So I can teleport multiple times at once, since that's not stated in Infernal Pursuit? What's the maximum number of attacks I can do? at lvl 20 max hp (see earlier chart), that's 18 possible attacks against.. everything? Holy shit. Nevermind, fuck my spells, I'll do that. Someone give me a magical weapon of awesome, I'll go kill Tiamat right fucking now! Yikes dude. 
That's ballistic, that's double the amount of attacks a fighter can do in a turn, for ONLY half the HP max used. Now let's farm lvl 7 spells for the victory and we're done here.


I love your ideas Ben, I really do. Seriously. But this is the problem with a HP based mechanic, you can abuse this to NO end.
Unless you layer this so HARD with addendum and fine print, it's going to be a bitch to regulate. If you make it decent for a max HP character, what about someone that only ever rolls 1's on his HD and has +2 HP from con? That's less than 100 hp, he can never risk using abilities to do shit all without just falling over to the first stiff breeze.
I love the idea, a bloodmage has been something that I've seen made around 5 times in 5e so far, and I have yet to see it be able to function the way it needs to. This is just due to the HP mechanic. I've seen it made as a sorc archetype, as a barb rager, and now three times as a stand alone class. The abilities all differ, but it always has the hp = spells aspect. And that aspect is too easy to break or be broken (UP/OP) by simple character selection.

Yeah man, the restrictions with mobiles can be a pain.
New mechanics and styles can be done, it's just an over time balancing effort. You just picked one of the hardest mechanics to ever balance for this lol ?

Heehee, I was wondering when you'd find time to post back

As a side note for a broken combination I just noticed, I'd like to multiclass this with a lvl 10 necromancer, using their lvl 10 ability as follows:


Just destroyed that mechanic

Sorry, I'll go back to my corner now..