by Painkeeper
Apparently, unless I'm missing something, the guard ability can be used to prevent the destruction of another unit selected as a toll for the attrition die.Rules, page 9 - Attrition Die wrote:
[...]
For each skull symbol on the die, the player must destroy that many of his participating units. (Destroyed units are immediately removed from combat and do not contribute their strength during combat resolution; see page 14.) If a unit’s ability prohibits it from being destroyed in combat, the player must choose another participating unit to destroy. If there are no other participating units, then no units are destroyed.
For each skull symbol on the die, the player must destroy that many of his participating units. (Destroyed units are immediately removed from combat and do not contribute their strength during combat resolution; see page 14.) If a unit’s ability prohibits it from being destroyed in combat, the player must choose another participating unit to destroy. If there are no other participating units, then no units are destroyed.
I think that the clause referring to some units destruction immunity doesn't stand here, because oft he quoted text prevent that particular unit to be selected. Instead, the Guardian's ability acts later: when you already have condemned (selected) a viable unit, then you can save it for the duration of the fight.