DR that stacks

[DiscOH]

The Armored Defense of the Armor Master:

Spoiler:

At 5th level, an armor master gains DR 1/— when wearing light armor, DR 2/— when wearing medium armor, and DR 3/— when wearing heavy armor. At 19th level, this damage reduction increases to DR 4/— when wearing light armor, DR 8/— when wearing medium armor, and DR 12/— when wearing heavy armor. This damage reduction stacks with that provided by adamantine armor, but not with other forms of damage reduction.

And adamantine:

Spoiler:

Armor Armor made from adamantine grants its wearer damage reduction of 1/— if it's light armor, 2/— if it's medium armor, and 3/— if it's heavy armor...

Clearly stack.

The stalwart feat:

Spoiler:

While using the total defense action, fighting defensively action, or Combat Expertise, you can forgo the dodge bonus to AC you would normally gain to instead gain an equivalent amount of DR, to a maximum of DR 5/—, until the start of your next turn. This damage reduction stacks with DR you gain from class features, such as the barbarian's, but not with DR from any other source.

Stacks with class features (such as Armored Defence).

Does stalwart stack with adamantine while stacking with armored defense?

Regardless, what other convoluted forms of DR stacking exist?

[DiscOH]

bump?

[Sazbirtraz]

In this case, you would get either Armored Defense + Adamantine or Armored Defense + Stalwart, whichever is higher (probably Stalwart unless you are Combat Expertising at lowish level).

The DR gained from Adamantine interacts with a class feature in the case of Armored Defense, but is not in itself a class feature, so by definition cannot stack with Stalwart.

[DiscOH]

Could stalwart stack with two separate class features?

(for instance invulnerable rager and stalwart defender)

[VM mercenario]

DiscOH wrote:

Could stalwart stack with two separate class features?

(for instance invulnerable rager and stalwart defender)

Yes but they wouldn't stack with ech other so, again, stalwart plus invulnerable rager DR or stalwart plus stalwart defender DR. Can't stack the three.