I was thinking of fielding a metal slan hence my question. What happens if I cast Glittering robe on a unit of Krokxigores? Will they have 5+, 4+ or a 2+ save?
This has been discussed with Saurus and I believe the consensus is that the Scaly Skin from the spell replaces the units' existing Scaly Skin. Or unit would have Scaly Skin (5+) twice with no stacking. Either way, the Saurus would still have 5+ rather than stacking to 3+. For Kroxigor, it is a little different since the spell's save is worse than what they have naturally. I suppose some could argue that RAW the Krox would have 5+, but that seems unreasonable to me. I would say that the spell does not replace the existing Scaly Skin (4+), but that the unit has both special rules. Nothing in the rules indicates that Scaly Skin can stack, so you take the better of the 2 saves. Bottom line, IMO, they have 4+.