[Peter Ebbesen]

You say that your opponent's Cyclops Tartarian costs him 12 death gems and 15 nature.

If this is the case, there is no way you need 100 communion slaves to stop him as that is a Cyclops without equipment (and we are ignoring all the "bad" Tartarians he has received, which raises the actual average cost of fielding a strong deployable Tartarian like the air-earth Cyclops).

More to the point, you didn't note in your first post that your problem was merely stopping an air-earth Cyclops, just that you had problems facing rain of stones hitting a 100-man strong communion, something that Verjigorm helpfully answered.

So we have two possibilities:
1) Your problem is how to kill a Tartarian who casts rain of stones and you have used a really bad approach; Your real problem in this case is not how to manage communions, it is how to kill Tartarians. Change your strategy.

2) The Tartarian is just part of a force you were facing with a monster communion that made sense in the circumstances (100 man strong communion? Just what were you doing? Even master enslaving can be done very reliably with 32+ S1 communion slaves and PotS+LotNS) and your real issue is how to survive Rain of Stones or other battlefield damage spells that hit in combat round 1 when you are on the attack. Verjigorm has given you a good answer to this - spend the gems necessary on forging armour for each and every communion slave you want to survive (And use Dwarven Hammers to cut the cost down to 3 gems per piece of armour)

If 2) is the case and your gem economy cannot handle creating the items needed, then trying to assemble a 100-man strong communion and using that as an offensive force is really bad strategy on your part and you should come up with another way to deal with your opponent or to get him to use up his gems before your main force hits.