No DC if the mourner can't take anything with it for Shadow Walk.
I just have to say this is one of best creatures I've seen in a while. It hits all of the ABCs of monster creation: artistic, balanced, and cohesive.
And now I've got that song stuck in my head...
Thanks :-)
P.S.
How about this ability:
Aura of Grief (Su): Every round that an enemy remains within 20 feet of a mourner in black, he or she must make a Will save (DC 17 ) or be overcome with grief and regret, becoming unable to move or attack for 1d4 rounds. Victims may still defend themselves, however. A successful save renders the subject immune to that mourner in black's aura of grief for 24 hours. The save is charisma-based. This ability only affects living creatures with an Intelligence of 3 or more.
Debby