Not that we didn't know that Belkar was evil, but I wonder how he plans to use that thing if it hurts him when activated...
Or maybe he'll use it to expose Durkula for beung evil.
They can. However, by the 3.5 rules, Detect Evil detects "Undead" not "Evil undead"..
Also, can't free-willed undead be any alignment they choose? I seem to remember an entry for good-aligned elven liches somewhere.