[Edi]

The Lord Guardian of MA Ulm has an ability that is named Halt Heretic, which works like awe against enemy sacred units. I do not know whether the Halt Sacred weapon effect does the same thing (presumably results in a morale check or lose action next turn if it hits, which would be the same).

Both of those are different from the Black Halberd's Bane of Heresy secondary effect that does aoe AP fatigue damage.