[Verjigorm]

Communion slaves (Pythian) and Blood slaves are quite fragile and are frequently the target of big AoE since you can easily nullify a big communion with such a spell while leaving your own, presumably more well-armored, units only lightly scratched.

Generally, when you have a solid communion protecting the members of that communion with some basic armor is usually a good idea. It costs a few gems, but I mean, how many gems are you spending on that one SC right?

Here are some nice items for communicants (this doesn't work for blood slaves--they always die and, therefore, one should never rely on blood magic as a primary tactic as it will fail you once your opponent figures it out). There's no way to protect a bevy of Sabbath Slaves, don't bother. Keep them in your lab for ritual magic. Taking them into combat is dangerous and you should only expect to be able to use them for 1 turn. After that, they're likely to be dead from AoE if your opponent is aware of what you are doing. As a surprise attack you're probably ok, though.

You want Cheap and Effective for equipping communicants. 1 item each, preferably of 5 gem cost and preferably a "cheap" gem which means what... Air gems! Fortunately, air magic has that going for it:

Light Weight Scale Mail (Ax5): Probably the cheapest thing you can put on them. Unfortunately, has 1 encumbrance.
Weightless Scale Mail (Ax10): 0-enc version of above
Shambler Skin Armor (Wx5): Delicious water breathing bonus
Rainbow Armor (Ax5 Nx5): If you can make it these are the bomb with Reinvig +3 and MR+3

Shroud of the Battle Saint (Sx5): IMO, this is the king of mage armors since you can commute your bless effect with it and it's only 5 gems. Unfortunately those gems are astral pearls, but hey... If you have an E4N4 bless you're golden or even just one of the above. A4 gravy is also nifty.

Robe of Shadows (Sx10): I would usually go for the Shroud instead unless you have a 3-path rainbow tender with no significant bless and a lot of extra pearls.