Undead Whenever this unit takes a morale test it is passed automatically. Then roll as many dice as remaining models/tough in the unit, and for each result of 1 the unit takes one wound, which can’t be regenerated.
Tough(X) Models with this special rule must accumulate X wounds before being removed as a casualty.
If a model with Tough joins a unit without it then you must remove regular models as casualties before starting to accumulate wounds on the model with Tough.
When a unit with multiple Tough models takes wounds you must accumulate them on a single model until it is killed before starting to accumulate them on another.