[DrPraetorious]

One thing not mentioned in this article is the benefit of armored communions.

Communion masters generally carry valuable gems, possibly penetration boosting items, and seldom have to worry much about fatigue, obviously. So it's generally a good idea to protect your investment (vs. stray arrows, for example) by putting them in some armor.

This also goes to the question of how to protect a valuable communion if you are very communion dependent (for example, as Pythium or Ermor or Bogarus).

* Rune Smashers, Eyes of the Void and Spell Foci are all great for masters casting Shadow Blast or groovy stuff like master enslave.
* Masters spamming elemental attack spells want boosters, not for fatigue reduction, but for increased damage and/or area of effect. This is obviously true for most of them (note all the +s in the spell description) - what most people don't know is that the fatigue inflicted by the secondary wave (which is area 9!) from thunderstrike is also air-magic-dependant, so if you can push your air magic up higher it becomes much more devastating.
* A communion matrix is often a good investment even for a communion master who has astral. +1 turn of spell casting is a huge advantage, and for a big-spell communion, it is not expensive.
* 50% resistance to fire and cold more or less assure that you won't go down to a murdering winter or flames from the sky. Various combinations of armor and misc items grant this, but fire plate and a ring of ice is probably the cheapest way to go.

In the late game, murdering winter/flames from the sky are a virtual surety. If you have the Forge, absolutely forge fire plate and a ring of frost for each and every slave.