Const. based combat feats

[BDEYE]

Strength and Dexterity both get good feat trees that offer new tactical options and possible character builds. Constitution get Endurance and Diehard. We've got to be able to do better then that. These are just a few ideas, I'd be curious to see what other folks can come up with. I'm not looking for anything complicated, nothing that couldn't appear in the core book.

Improved Diehard:
Prerequisites: Constitution 13, Diehard
Whenever you are reduced to anywhere from -1 to -9 hit points, you gain fast healing equal to your Constitution modifier until you have at least 1 hit point.

Battle Hardened:
Prerequisites: Constitution 13, BAB +1
You may add your Constitution modifier to your AC rather then your Dexterity modifier.

Tireless:
Prerequisites: Constitution 13, Endurance
If you and an opponent threaten one another in melee combat for three continuous rounds, you can make a contested Constitution check against that opponent as a free action. If you win the check, you gain a bonus to your attack roll equal to your Constitution modifier on the fourth round and every subsequent round until the opponent is no longer threatened by you. This bonus does not apply against Undead and Constructs.

Pressure:
Prerequisites: Constitution 13, Tireless
You may make a 5-foot step into a square occupied by an opponent against which you have a Tireless bonus. If you do, that opponent must move backwards 5 feet and cannot make a full attack the next round. Other combatants can make attacks of opportunity against you and the opponent whose space you enter as normal.

Exhaust:
Prerequisites: Constitution 13, Tireless
If you have gained a Tireless bonus against an opponent for three continuous rounds, on the fourth round you may make an Overrun attack against that opponent with a +4 bonus to the attack roll and without provoking an attack of opportunity. If the Overrun is successful, you get a free attack against the same target you just Overrun, and if this attack hits it automatically does damage as a critical hit.

[Duke of URL]

Battle Hardened:
Prerequisites: Constitution 13, BAB +1
You may add your Constitution modifier to your AC rather then your Dexterity modifier.

The others I like, but this seems flat-out broken. DEX is frequently a dump stat for heavily armored characters of any class (yes, I'm looking at you, Cleric), whereas no one willingly dumps CON. Figure this is a permanent +2 to +3 AC boost -- probably even higher for a non-DEX fighter or barbarian. It also would lead to a lot more folks dumping DEX for CON, even if they aren't heavily armored -- you gain extra HP, AC, and Fort save for a loss in Reflex save and DEX-based skills -- a good deal for just about anyone other than Rogue-types. Even Wizards and Sorcerers would likely choose to pump CON over DEX with this feat.

Just from a mechanics standpoint, do you retain this bonus if you would normally be denied your DEX/dodge bonus? If so, this makes it even more broken, if not, then why not, since it is no longer reaction-based.

[Roderick_BR]

I like these.
Improved DieHard: Not bad, means that you can only die in battle if someone hits you untill you stop moving. Should require a high BAB.
Battle Hardened is not that bad. I think I saw some variants in some books. Just add some high requisites. I mean, battle hardened means someone experient in battle, so he should need a higher BAB.
Maybe make it work only on meelee? Dosen't make sense to work on ranger/magic attacks.
Tireless... I think there are some feats already that allows you to gain bonus on extended battles. I'll have to check it.
Pressure may get broken, because it gives you a auto-success bullrush. Make it that it grants you free bullrushes attempts instead, everytime you hit.
Exhaust is interesting, but sounds weird. The effect sounds more like a power attack thing. I was thinking about making the opponent make Con/Fort checks, or getting tired/fatigued. A bit like a pugilist tires an opponent.

[RelentlessImp]

Suggestions for Battle-Hardened:

Raise the requirements to: Endurance, Diehard, BAB +3.
Or
Make it a flat Damage Reduction of ConMod*1.5(round down)/- that stacks with other damage reductions.

Most definitely, if you keep it the way it is, make it so you lose it when you would be denied a dexterity bonus to AC (even the most battle-scarred warrior can be taken down if he's caught unawares, such as being flat-footed or surprised).

The others look good, though. I especially like the Tireless tree.

[Zeta Kai]

I agree with the above suggestions, but I also really like the core concept being presented here. So I've attempted a minor rewrite. How this:

Improved Diehard [General, Fighter]
Prerequisites: Constitution 13, BAB +5, Diehard
Benefit: Whenever you are reduced to anywhere from -1 to -9 hit points, you gain Fast Healing equal to your Constitution bonus (if any, minimum 1) until you have at least 1 hit point.

Battle Hardened [General, Fighter]
Prerequisites: BAB +5, Endurance
Benefit: You may add your Constitution modifier to your AC rather then your Dexterity modifier. If you would normally be denied a Dexterity bonus to AC, then you lose this bonus as well.

Tireless [General, Fighter]
Prerequisites: Constitution 13, Endurance
Benefit: If you & an opponent threaten one another in melee combat for 3 continuous rounds, you can make a contested Constitution check against that opponent as a free action. If you win the check, you gain a bonus to your attack roll equal to your Constitution modifier on the 4th round & every subsequent round until the opponent is no longer threatened by you. This bonus does not apply against Constructs or the Undead.

Pressure [General, Fighter]
Prerequisites: Constitution 13, Tireless
Benefit: You may make a 5’ step into a square occupied by an opponent against which you have a Tireless bonus. If you do, that opponent must move backwards 5’ & cannot make a full attack the next round. Other combatants can make attacks of opportunity against you & the opponent whose space you enter as normal.

Exhaust [General, Fighter]
Prerequisites: Constitution 13, Tireless
Benefit: If you have gained a Tireless bonus against an opponent for 3 continuous rounds, on the 4th round you may make an Overrun attack against that opponent with a +4 bonus to the attack roll & without provoking an attack of opportunity. If the Overrun is successful, you get a free attack against the same target you had just Overrun, & if this attack hits, it automatically does damage as a critical hit.

[brian c]

Battle Hardened [General, Fighter]
Prerequisites: Constitution 13, BAB +5, Endurance
Benefit: You may add your Constitution modifier to your AC rather then your Dexterity modifier. If you would normally be denied a Dexterity bonus to AC, then you lose this bonus as well.

That's a little better. It can probably do without the 13 Con prereq though; if you don't have a good Con score then you wouldn't take the feat anyway.

[BDEYE]

Zeta Kai, thanks for rewriting and formating these right, this is my first attempt at homebrewing feats. I think that the BAB bonus for Improved Diehard should be a notch lower just to make it more available to Monks and Rogues. I agree that Battle Hardened shouldn't apply if you're flat footed, and I further messed with the feat to balance it for people who dump everything into Constitution, as well as to give incentive to people to make builds with high Constitution and high Dexterity both, _and_ to make it clear that you can use it with highly armored characters.

I think I came up with a more elegant approach for the Tireless feat tree, tell me what you think. I also added a couple more feats around this general concept. I'm still trying to come up with things that provide new options, and aren't just purely reactive.

Improved Diehard [General, Fighter]
Prerequisites: Constitution 13, BAB +4, Diehard
Benefit: Whenever you are reduced to anywhere from -1 to -9 hit points, you gain Fast Healing equal to your Constitution bonus (if any, minimum 1) until you have at least 1 hit point.

No Pain [General, Fighter]
Prerequisites: Constitution 18, BAB +12, Improved Diehard
Benefit: You are immune to critical hits.

Elbow Grease [General, Fighter]
Prerequisites: Constitution 13, Endurance
Benefit: If an opponent gains an attack of opportunity against you because of an attack you executed (such as Trip, Disarm, Bull Rush, or firing a ranged weapon while threatened) and hits you, you may roll a Fortitude save where the DC is equal to the damage inflicted by the attack of opportunity. If you make the save, you can still execute the attack despite being hit.

Battle Hardened [General, Fighter]
Prerequisites: BAB +5, Endurance
Benefit: You may add half of your Constitution modifier, rounded up, to your AC as a circumstance bonus. If you would normally be denied a Dexterity bonus to AC, then you lose this bonus as well.

Tireless [General, Fighter]
Prerequisites: Constitution 13, Endurance, BAB +1
Benefit: If you & an opponent threaten one another in melee combat for 3 continuous rounds, you can make a contested Constitution check against that opponent as a free action. If you win the check, your opponent becomes Fatigued.

Pressure [General, Fighter]
Prerequisites: Constitution 13, Tireless
Benefit: Whenever you hit a Fatigued or Exhausted opponent in melee combat, you may make a 5’ step into a square occupied by that opponent. If you do, that opponent must move backwards 5’ & cannot make a full attack the next round. Other combatants can make attacks of opportunity against you & the opponent whose space you enter as normal.

Exhaust [General, Fighter]
Prerequisites: Constitution 13, Tireless
Benefit: If you and an opponent threaten one another in melee combat for 3 continuous rounds and that opponent is fatigued for all 3 of those rounds, the opponent becomes Exhausted.

Outlast [General, Fighter]
Prerequisites: Constitution 13, Exhaust, BAB +6
Benefit: When you hit an opponent who is Exhausted in melee combat, your attack does damage as a critical hit. The opponent must make a Fortitude save where the DC is the damage inflicted by that hit. If they fail, they fall prone and become Confused for 1d4 rounds.

[Zeta Kai]

Much better. You're right, these are elegant, & also rather yoinkable now. I was going to say that No Pain was broken, but then I noticed the prerequisites. It should be fine. It may still be a little overpowered, so you could try the following:

Benefit: Any critical hit that strikes you is dulled by one multiplier; 2× criticals deal normal damage only, 3× criticals deal 2× instead, & 4× criticals deal 3× instead.