[RPG] How to get a character with the lowest hit points possible

This is an extremely arbitrary change that will break a lot of the intended functioning of the system

The system is designed with certain HP values in mind. Damage scales rapidly with level, in fact faster than HP does, and thus after only a few levels past the cap, just about everything will kill in one shot.

The system was already broken though.

Enough optimization, and most melee types can one-shot just about anything of a remotely appropriate level that they can get their hands on. This just makes doing that much (much) easier.

Ultimately... perhaps it would “work.”

But most players don’t play at those optimization levels, and most combats are not supposed to be decided by initiative, even if at the highest optimization level that’s often what it comes down to. Gentlemen’s agreements, ban lists, houserules, usually they’re designed to mitigate if not eliminate the rocket-tag nature of D&D, while this would put it into overdrive.

It would be very strange, and extremely lethal. Death would be common, and would frequently be arbitrary. Characters will often die without actually getting a turn in which to do anything to try to prevent their death. Ambushes would be almost impossible to survive; a single rogue archer getting a full-attack before anyone else has gone (i.e. they’re flat-footed), or from a hidden location, could easily kill the entire party in one turn. Initiative would be, by far, the most important combat stat (which it arguably already was), because whoever goes first, will kill the enemy before that enemy can go, most of the time.

Which doesn’t sound like an overly fun game to me, but I gather some do prefer it. As I said, at high enough optimization levels you can force the game into that mold anyway. At least this change eliminates the “skill gate” for you to get in on the super-lethal combat.

If that’s what you want, and more importantly, if you can find players who want that, maybe it could “work,” for a given definition of working. I wouldn’t play, I don’t think I know anyone who would be interested in playing it, but maybe you can find them.

But you perhaps misunderstand HP

Based on this comment:

But there are other solutions - give PCs so many free rerolls (favors from the Gods...) for each adventure (or per level), something used in Deciphers's LOTR RPG. Or be generous with magic armor & shields. Magic armor is a good proxy for extra hit points, minus all the hand-waving trying to explain how a PC can survive unbelievable amounts of damage.

I think you are misunderstanding the breadth of HP’s abstraction: it does not (necessarily) represent physical health, nor does lack of it (necessarily) represent injuries and wounds.

It also represents favors from gods, innate magic, destiny, luck, morale, and so on. Damage can be done from a lot of causes, and it can also be healed in a lot of ways (there are healing effects that derive their effect from inspiration, for instance, and some of those are extraordinary, i.e. nonmagical, in nature). HP is a large and expansive abstraction, but it’s not just “characters can soak absurd numbers of wounds and injuries.” It’s often closer to “plot armor.” Note also that loss of HP does not result in penalties due to wounding. Part of that is simplification and cinema, but part of it is also an acknowledgement of what HP is not, namely wounds and injuries.

Vastly superior option

As everyone has been saying, E6 is the way to go. E6 allows you to maintain that “low-level” feel, capping players at 6 class levels (and that includes 6th-level HP), but allows them to continue to gain XP, which they can trade in for bonus feats. It’s a great system, giving just enough to keep the game moving and the characters growing, while preventing more powerful effects that greatly change the nature of the game from getting into play.

Disclaimer: The maximum theoretical answer is... as much as you want. An example being Pun-pun. Since those are not playable, this answer focuses on how getting a high Charisma without completely breaking the game.

Total: 99.

Starting from the basics:

• Base Charisma score 18
• Leveling points +5
• Inherent bonus +5
• Venerable +3

thus a minimum of 31.

A little cheese to sweeten the deal:

• Lesser Aasimar for +2; type is Humanoid (Planetouched)
• LA+0 Magic-Blooded template (Dragon Magazine #306, p. 50) for +2; type unchanged
• LA+0 Unseelie Fey template (Dragon Compendium, p. 224) for +2; type changes to Fey
• LA+1 Draconic template (Draconomicon, p. 150) for +2; type unchanged
• LA+2 Half-Fey template (Fiend Folio, p. 90) for +4; type changes to Fey or if you prefer Obah Blessed template (Dragon Magazine #136, p.60), same bonus, type unchanged
• LA+5 Suel Lich template (Dragon #339, p. 60) for +2; type changes to Undead
• Polish with a bit of bloodline, such as the Celestial Bloodline (Unearthed Arcana, p.21), granting +1 at level 9

thus a bonus of +15.

Our type is now Fey (Planetouched), unless using Suel Lich, however taking the 1st-level feat Human Heritage (Races of Destiny, p. 152) turns it back to Humanoid (Human, Planetouched). It requires us to be of a half-human or human-descended race, I expect Lesser Aasimar to qualify, otherwise, what's the non-Aasimar part?

I prefer cheese with my cheese:

• The Worm of Minauros magical location (Fiendish Codex II, p. 49), for +1 unnamed bonus; to be renewed every 30 days by committing an act of obeisance (if non-lawful) or a corrupt act (if non-evil)
• A Pact with the Devil (Fiendish Codex II, p. 23), for +1 unnamed bonus; it tends to lead one toward damnation

thus another +2.

Picking the right classes:

• A single level in the Dragon Devotee class (Races of the Dragon, p. 84), for an unnamed +2.
• A single level in the Anointed Knight class (Book of Exalted Deeds, p. 49), for the Divine Clarity oil and an unnamed +1.
• A single level in the Half-Water Elemental class for a racial +2 (Dragon #326, p. 89)
• Two levels in the Half-Air Elemental class for a racial +2 (Dragon #326, p. 87)
• Three level in the Half-Fire Elemental class for a racial +2 (Dragon #326, p. 88)
• Four levels in the Ghost savage progression (http://archive.wizards.com/default.asp?x=dnd/sp/20040117a) for an unnamed +4.
• Six levels in the Warchief class (Miniatures' Handbook, p. 24), for an unnamed +6.
• Eight levels in the Doomlord class (Planar Handbook variant, p. 47) for an unnamed +2.

thus another +21.

Picking the right feats:

• Ability Enhancer (Dragon Compendium, p. 91), enhances the ability bonus of any Transmutation spell by another +2.

Picking the right spells:

• From Zachiel's list, the Paladin's spell Righteous Aura [Abjuration] (Spell Compendium, p. 177) for +4 sacred bonus to Charisma; to be persisted.
• The Bard's spell Snowsong [Enchantment] (Frostburn, p. 105), for +4 Morale bonus to Charisma; to be persisted.
• The Cleric's spell Visage of the Deity, Greater [Transmutation] (Spell Compendium, p. 231), for +4 unnamed bonus to Charisma (if Good); to be persisted.
• The Bard's spell Nixie's Grace [Transmutation] (Spell Compendium, p. 148), for +8 enhancement bonus to Charisma; to be persisted.

thus another +20, or +24 with the Ability Enhancer feat.

For persisting Bard spells, Divine Metamagic does not work; an Incantatrix (Player's Guide to Faerûn, p. 61) can, however, persist spells either through Cooperative Metamagic (2nd-level) or Metamagic effect (3rd-level).

Buying the right items:

• The Command armor property (Defenders of the Faith, p. 23), for a +4 Competence bonus to Charisma.

thus another +4.

Knowing the wrong persons:

• A Lilitu's Gift (Fiendish Codex I, p. 43), for +2 Profane bonus to Charisma, to be renewed every 24 hours. Makes alignment drifts toward Chaotic, perfect to balance the Worm of Minauros!

thus another +2.

For now, that's a grand total of 99.

Of course, how to manage a deal to get all those is an exercise for the reader... A Cleric/Sublime Chord/Eldrich Master with the Alternative Source Spell feat could get most of it I'm told, which would most probably be foregoing a few of the suggested classes (starting with the Doomlord).

Among other things, I picked ideas from Ways to increase Charisma?, which includes some builds and The most cost effective way of boosting charisma? and I have not read them fully.