Leper

Many will fall in the face of chaos, but not this one— not tod-  D E A T H  B L O W

… and yet even the mightiest hero can be felled by means as mundane as death within one’s own body.

It's an adaptation of the class from darkest dungeon. Everything here pretty much sells the there they were aiming for. Not saying it remains without issues however

so what happens when the cleric casts greater restoration on you >_>

3rd Level. I'd really rather Leper's Bell not have a random round duration, they're a pain to track in play and 5E has largely done away with them. Instead, you can crib either of the Paladin Channel Divinity effects that cause fear, with some subtle alterations:

Leper's Bell

The tolling of the leper's bell invokes the inevitability of death for all who hear. As an action while holding the bell in one hand, you can ring it to force each creature within 30 feet of you that can hear you to make a Wisdom saving throw (DC equal to 8 + your proficiency bonus + your Strength modifier). On a failed save, a creature becomes frightened of you for 1 minute. The frightened creature can repeat this saving throw at the end of each of its turns, ending the effect on itself on a success. If the creature succeeds on its saving throw, it can't be effected by this feature again for 24 hours.

With the broader range and indiscriminate effect, there's some risk to allies unless you "inoculate" them pre-combat. It's a big punchy feature, but it's basically the only thing you're getting at this level. I say that because you can't get proficiency with a healer's kit. It isn't a tool and rather than make rolls with it (the point of proficiency) it's used to automatically pass a Wisdom (Medicine) check to stabilize a target. You could give them proficiency with the Medicine skill, or you could somehow enhance their use of the kit, but you can't grant tool proficiency for things that aren't tools.

In contrast to the bell, the Mask's benefits aren't nearly as compelling. Its essentially just more/bigger numbers, rather than doing anything to develop a theme or play-style. The easy solution is to cut the mask feature entirely to streamline the archetype. To the extent that you're committed to having both, i'd re-examine the thematic contrast you're trying to create between a Mask Leper and a Bell Leper to try and find something interesting about the Mask.

7th Level. Conventionally this level should lean heavily on the exploration and interaction pillars of the game. I like the concept and implementation of Dulled Nerves (though I don't see why they get acid resistance ), but I don't think it fits the curve to put it here.

10th Level. The problem with giving the Hunter Ranger's Multiattack feature to a Fighter, is that they have an additional extra attack, where the Hunter got this instead of an additional extra attack. Ranged builds can trivially take advantage of this, but even PoleArm Masters can find two targets in 10' it's because otherwise the fight is already over. I think your intention with Expanded Strike was something closer to the Arcane Archer's Curving Shot or the Hunter Ranger's Horde Breaker, to bring it back in that direction you'll need some other limitation on when it triggers.

If that wasn't the only problem, it also does nothing to advance the concept of "The Leper". Why does the diseased outcast get whirlwind attacks? I'm sure there's something more thematic you could pick up here. My advice is just to cut this completely and move Dulled Nerves up to here, but it's possible there's some other thematic feature you have in mind.

15th Level. Bleh, I don't at all care for Lost Senses. A big blob of maximum HP that doesn't change and Immunity to a damage type you're arguably suffering already. I'd absolutely agree that making the Leper "tanky" is a good choice, I don't think this is a good way to go about it. Maybe something that gives a small amount of temp HP whenever you lose hit points, maybe you've got a different interesting idea. This is the opposite problem of your 10th level feature; that was mechanically robust (if too strong) but with no narrative justification where this has solid story justification but the mechanic is uninspired. 

18th Level. Quite a few people have already mentioned the incentives to multi-class out but I can't help but bring it up again. Even discounting the janky off-schedule 20th level death sentence, the penalty of 18th level is so severe as to be nonsensical. It doesn't sell the story of the archetype, it doesn't excite the player about advancing; nearing the apex of the campaign this is a feature that says "just stop playing".

Conclusions. This is an archetype that intrigued me near the beginning and completely lost me by the end. I was expecting to see something that harmed creatures who touch you, inflicting a small amount of poison damage or the poisoned condition; something that was in keeping with the untouchable nature of a Leper. I wasn't expecting the Bell but the you did a good job selling me on it in the description. Unfortunately you didn't sell me on much else of the implementation. I'd suggest taking another shot at this because it remains a fascinating concept.

I think the multiclassing issue for Final Breath could be fixed if you changed the wording so that it would specify it means 20 levels total.However, I still think it should be changed, to give the player at least some time to use their character at 20th level before they die, for example the fighter may pass away after 1d6 months after reaching the level. 

To be honest, though I think that Eleventh Hour would be more discouraging to players than Final Breath as it cripples your whole party who need to be healing you all the time, which is especially bad since you have a huge amount of hit points to restore and they can't use anything that involves touching you so Healer feat, Cure Wounds and Lay on Hands are all out of the question. 

Also, I don't get how are you supposed to mark an enemy with a bell. Like what does your character actually do to achive that? 

It seems to be a display issue in general as I can't see those features on desktop either.. 

I agree with some of the balancing/mechanical points made above, but overall think it's an interesting class story-wise :)

Seems like a display issue on mobile. I can't see either of those abilities on my phone; they're just not there for some reason. Sorry for the hassle.

Am I missing something? The only abilities I see from the mask/bell seem to be alerting others of your presence/hiding your affliction. These are both cool touches for roleplaying, but from a mechanical standpoint don't really have any weight. Once again, compare some extra flavor to things like eldritch knight getting cantrips and first level spells at third level. Unless there's something I'm missing, from a mechanical standpoint there is essentially no 3rd level feature besides a single proficiency.

I really like this, but my biggest problem is there essentially isn't a level three ability. I like the flavor behind the mark and think you should keep it, but literally the only actual feature you gain is proficiency with a healers kit. Is that occasionally useful? Yes, but it's not a defining class feature. Eldritch knights get to cast spells at level 3 and brutes deal 1d4 extra damage on every attack. I would add another feature that can be more universally helpful. Maybe give 1-2 extra hp per level. If you do that I think you should replace Lost Senses with another small feature to show durability, like second wind providing resistance to bludgeoning piercing and slashing for one round.

I really like the idea behind this class.  Only thing I noticed for improvement is that the abilities appear to be in the wrong order :).

The idea of a very durable man afflicted with a terrible disease is a compelling one. It could also have really good story implications. How does he act in public? Does he keep himself separate from others as best as possible? Is he solemn and religious in the face of disease? Or is he hoping to revel in his last days?

This also reminds me of the Leper from the Darkest Dungeon. Was that your inspiration?

but despite the compelling idea of this class and the potential homage to another great game, the instant death at the end is definitely a huge downside that turns me away. How about instead of an instant death, give the Leper some sort of crippling affliction. Permanent disadvantage on certain checks such as Dex or Con saves? I believe that would thematically exemplify the leper’s disease without the terrible punishment of reaching pinnacle strength.

Also, a work-around for the final affliction would simply be to multi-class before level 20. Then you would not have the punishment for total class leveling. And giving players a restriction to multiclassing with this subclass would drive even more people away. 

Overall, I like the idea of the class and character role play involved. A change to the ending that would stay in theme would be a perfect change for this and make me really want to play this. 

Maybe not have an instant kill at level 20? I get that it is an important part of the theming, but it still feels strange to just instantly die right before what will probably be a big climactic confrontation.