Best special material for combatting undead?

[Ravingdork]

I'm thinking of a Knight of Lastwall using needle darts against the forces of the Whispering Tyrant.

What materials would be worthwhile for such a character to carry, and how much might they cost?

[Sibelius Eos Owm]

The only special material weakness found among undead off the top of my head is vampire weakness to silver. A silver or dawnsilver weapon like a holy avenger did wonders in my Carrion Crown adventure although I don't know how wide the utility might necessarily be for that one. Even so, TB has some nasty vampires in his service so not the worse of all ideas.

Alternatively if you're high enough level, peachwood is specifically strong against undead. If you don't have another way to beat a physical defense on hand (silver, bludgeoning, ghost touch etc) the peachhwood will get you at least a little edge in all circumstances... (but of course peachwood isn't very useful for needle darts... got carried away there remembering materials)

[Perpdepog]

It's not cheap, or easy to find, but you can also try Sisterstone. You'll need to either have a pair of items made out of it or a companion who is carrying it, though.

[Guntermench]

Duskwood/Peachwood are good, but they are unfortunately not metal.