Flagellant warbands are viewed with a mixture of fear and disdain by more level-headed soldiers.
As a result, few are willing to fight amongst their ranks.
A unit with this special rule can be joined by a Lector of Sigmar or a Priest of Sigmar.
However, these are the only characters that can join this unit. A Lector of Sigmar or Priest of Sigmar that joins a unit of Flagellants is considered to have the Unbreakable special rule for as long as they remain with the unit.
Note that a unit with the Unbreakable special rule cannot normally be joined by a character without it. This rule provides an exception that represents the fanaticism of Sigmar’s priesthood.