I am looking for ways for a character to become immune to the (5%) chance of automatically failing a saving throw because of a natural one on the d20 roll.
Aside from the Knight class at level 17
You no longer automatically fail a saving throw on a roll of 1"
(PHB2 page 28)
and the feat Steadfast Determination
You do not automatically fail Fortitude saves on a roll of
natural 1
(PHB2 page 83)
I could not find further sources or effects.
I vaguely remember the claim of someone writing a post or article about the Knight class, claiming one can get immune to natural ones on saving throws at level 1 – so I suspect there might be items with that effect.
Sadly, I find it quite hard to find relevant information via Google based on the specific meaning of the generic terms used for the issue.
Question: are there further sources to remove the "natural 1 = automatically failed saving throw regardless of the save bonus" rule?
Best Answer
Take the Pride domain
The question mentions "the claim [that] one can get immun[ity] to natural ones on saving throws at level 1." I suspect that claim was made by a player familiar with the granted power of the Pride domain (Spell Compendium 278–9). It allows the creature to reroll the first natural 1 on a saving throw, but the reroll must be taken, even if it's again a natural 1. Thus the domain's granted power will usually do what's desired. Many gods make available the Pride domain (see here), and in some settings a cleric with no deity can pick the domain (as per Deity, Domains, and Domain Spells on Player's Handbook 32). The granted power can also be gained from the planar touchstone site Catalogues of Enlightenment using the feat Planar Touchstone (Planar Handbook 41–2) or maybe just the feat Touchstone (Sandstorm 53). And, because this is D&D 3.5, undoubtedly other ways exist to gain that granted power, too.
Become a martial adept
Another alternative for avoiding rolling 1s on saving throws is the series of Tome of Battle maneuvers that replace a creature's saving throw with a Concentration skill check: the 1st-level Diamond Mind maneuver moment of perfect mind [counter] (ToB 64) for a Will save, the 2nd-level Diamond Mind maneuver action before thought [counter] (ToB 62) for a Ref save, and the 3rd-level Diamond Mind maneuver mind over body [counter] (ToB 64) for a Fort save. Each maneuver changes the nature of the listed saving throw into a skill check, and a natural 1 isn't an automatic failure on a skill check, but that natural 1 could still be a normal failure depending on the creature's modifiers. Martial scripts (ToB 147–8) aren't much use here, but many creatures may be able to benefit from such a maneuver by wearing a novice ring of Diamond Mind (ToB 149–50) (3,000 gp; 0 lbs.) or by taking the feat Martial Study (ToB 31–2).