Can slaves to darkness unit get a 6+ ward?

I noticed in the new battletome that pledge to nurgle units get a 6+ ward, which could turn into a 5+ if they already have a 6+. But I can't think of a way for a unit to have a 6+ already. Except the daemon prince.

There aren't any spells, manifestations, warscroll abilities that allow a unit to get a 6+ ward right? Maybe I'm missing something? Some units already have a ward or give wards that are already 5+ so it's redundant.

Am I missing something?