DR, Su or Ex?

[Rath the Brown]

IMO there are two types of DR - super-fast healing and toughness.

I agree with this; it says as much in the glossary of the Monster Manual and in the SRD.

The first set are supernatural DRs: all special material DR except adamantine, as well as alignment, magic, or epic.

What about the lycanthrope's damage reduction of 5 or 10/silver? That is one of the few that is specifically identified and it is listed as Ex.

 

[Philip]

When using a combo, such as a lich's DR 10/magic and bludgeoning, assume it is supernatural.

I don't think this is correct. Just dress a skeleton with a Mantle of Faith (which gives DR 5/evil). Effectively it now has DR 5/evil and bludgeoning. Then put up an Anti-magic Field. The skeleton drops back to DR 5/bludgeoning, not losing all his DR.

The lich would be DR 10/bludgeoning in the Anti-magic Field.