Spelleater with Undead bloodline

[NikolaiJuno]

The Spelleater Archetyp reduces it's class DR to 0 but The undead bloodline increases it to 8 at level 20.

Do they really stack legitimately? Because Undead would assume Base DR to be 5, but spelleater reduces that to 0. So the combination effectively adds 5 DR that shouldn't exist.

[Calth]

NikolaiJuno wrote:

The Spelleater Archetyp reduces it's class DR to 0 but The undead bloodline increases it to 8 at level 20.

Do they really stack legitimately? Because Undead would assume Base DR to be 5, but spelleater reduces that to 0. So the combination effectively adds 5 DR that shouldn't exist.

The wording of the undead capstone is bad, and should probably read increases by 3 rather than increases to 8. RAW you get the 8, but the RAI is probably a spelleater gets DR 3/-.