Is this Implacable Warrior homebrew fighter subclass balanced compare to other fighter subclasses?

Question

This was inspired by a previous question where the poster had mistaken what hit dice were for, thinking you could use them for a damage bonus. Which made me think...what if there was a class where you could use your hit dice for other things?

Hence the Implacable Warrior, a Fighter Subclass.

Design note: Hit dice are a scale-able resource but they don't regenerate in their entirety after a long rest. And with few at lower levels this may cause players to hesitate to use them. Hence this class also has 'determination dice' which go into the same 'pool' as your hit dice and act as a buffer, encouraging their use (especially as you get all determination dice back after a long rest).

---

Implacable Warrior

Your sheer determination powers you on against the odds. You are able to push on when others would fall by virtue of your iron will.

Indomitable Will

At 3rd level you gain proficiency in Wisdom saving throws

You also gain two determination dice. These dice are d10s. At 10th level and 15th level you gain an additional determination die (for a total of 4 at 15th level).

Whenever you spend a hit die, either to regain hit points after a short rest or for any of the features of this subclass, you may spend a determination die instead. You regain all determination dice after a long rest.

Focused Strike

At 3rd level, whenever you successfully hit a creature with a weapon attack, but no more than once per turn, you may spend a hit die. If you do so, roll the hit die and add the result to your damage roll.

Iron Recovery

At 7th level, whenever you use your Second Wind feature you may spend a hit die. If you do so you also gain temporary hit points equal to the result of the hit die + half your fighter level.

Retaliatory Strike

At 10th level, if a creature within your weapon range casts a spell that forces you to make a saving throw or successfully hits you with an attack roll you may use your reaction to spend a hit die.

If you do so, you immediately make a weapon attack against that creature. If the attack hits you may then either:

• add the result of your hit die to your saving throw if your retaliatory strike was triggered by a spell
• subtract the (result of your hit die + your fighter level) from the damage taken if your retaliatory strike was triggered by a successful attack roll.

Implacable Foe

At 15th level you refuse to lay down and die. When you are reduced to 0 hit points but not killed outright, you can use your reaction to spend a hit die. If you do so you drop to 1 hit point instead and gain a number of temporary hit points equal to the the result rolled + half your fighter level. However, your maximum hit points is also decreased by the result of your hit die.

Your maximum hit points are restored after completing a long rest.

Unstoppable Foe

At 18th level you have reached the epitome of the unstoppable warrior. Whenever you use any of the features of the subclass that allow you to spend a hit die, you may spend two hit dice instead (rolling both and using the total).

Answer 1

Indomitable Warrior's balance fluctuates.

Indomitable Will

Gaining 3rd save proficiency at such a low level is pretty good. It also has nothing to do with the rest of this feature, hence I would split the feature into two separate ones.

Re-purposing Hit Dice is this way makes it difficult to compare Indomitable Warrior with other classes and subclasses, because the only class resource that persists across long rests is the Hit Dice. In my experience it is very difficult for PCs to run out of Hit Dice, and actually running out of Hit Dice doesn't matter unless the next activity is a short rest. Hence a normal PC's resourcefulness is constant across consecutive long rests.

However, the Indomitable Warrior can easily run out of Hit Dice, and actually running out of Hit Dice matters as soon as you want to use one of your class features. Hence the Indomitable Warrior's resourcefulness is not constant across consecutive long rests. This means that if the Indomitable Warrior uses more than half its level of Hit Dice today, then tomorrow it will be less resourceful and therefore weaker.

The only subclass that behaves somewhat similarly in this regard the Berserker, for whom 'lack of Exhaustion' is effectively a class resource.

Moreover, usually some Hit Dice are in excess, by which I mean you don't need them to recover HP during a short rest. The value of most of the other class features improves if the Hit Dice used are in excess. More importantly, days that are not challenging will lead to more excess Hit Dice, which means that Indomitable Warrior gets more value from its features on those days, which is a weird dynamic to say the least.

Focused Strike

When the Hit Dice are in excess, dealing an extra 1d10 damage per turn (or 2d10 with a crit) is ok, but will falloff quickly as you level up. When they are not in excess, dealing the extra damage instead of 1d10+con healing is more or less an equal trade.

Iron Recovery

When the Hit Dice are in excess, gaining those hit points is decent. When the Hit Dice are not in excess, is a slightly advantageous trade.

Retaliatory Strike

There is too much going on in this feature. Subclasses usually introduce only one narrow trigger, but this feature introduces 2 broad triggers. You don't need to make the feature weaker, but you need to narrow its scope, especially because the next feature also uses reactions.

See the Monster Slayer's Slayer's Counter for reference of something similar.

Implacable Foe

This is a solid feature regardless of whether the Hit Dice are in excess or not, although parts of this feature are not be very significant: the temporary hit points, because at this level 15 or so effective HP will rarely lead to a different outcome than 1 HP; the max HP reduction, because it won't come into play unless you use this feature a lot and then receive massive damage.

For reference of something similar see the Zealot's Rage Beyond Death or the Long Death's Mastery of Death.

Unstoppable Foe

This feature is great only if the Hit Dice are in excess, otherwise it's kinda bad. Moreover, as you take advantage of this feature the Hit Dice will quickly stop being in excess.

Comparison with Battle Master

For the sake of comparing Indomitable Warrior with the Battle Master, I will assume that the Indomitable Warrior's resources consist of half its Hit Dice plus all its Determination dice (the other half of the Hit Dice are used during short rests, play testing will be necessary to determine if this assumption holds). The Battle Master's resources consists of its superiority die.

• Between levels 3 and 9 the Indomitable Warrior can use about as many resources as a Battle Master that took no short rests.
• Between levels 10 and 14 the Indomitable Warrior can use nearly as many resources as a Battle Master that took 1 short rests.
• Between levels 15 and 20 the Indomitable Warrior can use about as many resources as a Battle Master that took 1 short rests (not factoring Relentless).

Considering that the DMG recommends 2 short rests per adventuring day (in my experience 1 short rest per adventuring day is more common), the Indomitable Warrior does not have that many resources at its disposal. Moreover, Focus Strike and Iron Recovery are not better than Battle Master Maneuvers, whereas Retaliatory Strike and Implacable Foe are.

Overall Indomitable Warrior starts underpowered, especially between level 5 and 9. Then at level 10 it gets its first strong feature and an extra Determination die which bumps it up to balanced. However, the evaluation goes up:

• by a notch, if a combat day and non-combat days alternate;
• by half a notch, if two combat days and non-combat days alternate;
• by half a notch, on days that are not challenging.

By going up by a notch I mean underpowered to balanced, or balanced to overpowered.

Answer 2

No, and one major reason

Implacable Foe

At 15th level you refuse to lay down and die. When you are reduced to 0 hit points but not killed outright, you can use your reaction to spend a hit die.

I honestly find the use of hit dice hard to parse from a balance perspective, but not dying for up to 20 fatal blows is madness.

Compare to the zealot barbarian who won't die during a rage, but still counts death saves, so can still die after 3 hits if they don't get healed.

I know that a reaction is a once per round resource, but I don't think that balances it out.