Making Dragons Terrifying Again [3.5]

[afroakuma]

Here are a few homebrew feats you can use to dial them up a notch, though be wary about letting them slip over to players:

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Dauntless [Monstrous]
Your powerful stature is not easily afflicted by attempts to totally overcome you.
Prerequisites Con 21+, Huge or larger size
Benefit Whenever you fail a Fortitude save, you may reduce your current hit points by 100 to treat the effect as though you had succeeded on that save. This is not damage and is not subject to DR, other effects or abilities that would reduce or mitigate damage, or effects or abilities that trigger on hit point damage.

Monstrous Toughness [Monstrous]
Your endurance is indomitable and without peer.
Prerequisites 21+ HD, Con 21+
Benefit You gain an additional 100 hit points.

Resist Precision Damage [Monstrous]
You exhibit remarkable self-concern when it comes to your vital spots, helping you better protect them.
Prerequisites Natural armor bonus 10+
Benefit Halve the amount of any precision damage (sneak attack, etc.) dealt to you. Reduce the critical multiplier on attacks against you by 1 (to a minimum x2 multiplier).

Spell Aegis [Monstrous]
You are unaffected by certain specific magics.
Prerequisites Racial spell resistance 18+ or Spell Immunity, 5+ racial HD
Benefit Choose one spell per 2 HD you possess (maximum five spells) of a level no greater than half your HD, rounded down. When it would be beneficial to you, you completely ignore the effects of such spells as they pertain to you, save in such ways as would be physically irrelevant (you cannot ignore the rain and mud from control weather, nor pass through a wall of stone, nor cause a flying creature to crash to the ground).

Use Monstrous Toughness to increase the fight duration, Dauntless as a buffer against save-or-die effects, and Spell Aegis to selectively deny extreme "problem spells" (shivering touch being a big one).