[Jack Simth]

Probably an unintended consequence of how they choose to make magic items work, and how they chose to make communion work -

Suppose every magic item was a base item that cast some number of spells on some timing as though it were the caster casting the spell (combat turn (spirit helm's lightning), start of combat (Staff of Storms' Storm), combat use (Dragon Helmet's Fire BLast), tactical use (Gift of Kurgi's Send Horror), or whatever) and/or had an additive effect to some set of stats.

As Communion master/slave is just another spell, the Communion/Slave matrix could just serve to cast the appropriet spell on a "start of combat" timing.

Now suppose that the Communion/Slave matrix effectively happened before the spells cast from some other items:
1) the master/slave spells take effect
2) the other items cast their spells as though the bearer was casting them
3) any "self" spells from (2) cascade through the communion to the communion slaves.

If the Armor of Virtue cast "Ritual of Returning" on a combat start timing, that could explain what you see; a suggestion to test and see if that is how it works would be to attempt it using items which create spell effects (especially those which don't stack with the spells), such as a Robe of Invulnerability, Shadow Cloak, Fire Shield, or Air shield.

Oh, I just had a nasty vision - Conscious exploitation of this effect - Mass production of slave matrixes and Communion matrixes, a few items (Fire shield, cloak of invulnerability, air shield, Boots of Stone, Crystal Shield, maybe medallion of vengence, et cetera) placed on several masters (mages (or non-mages, even) with Crystal Matrices), who then just hang out in the back (or even retreat), while the communicants (cheap scounts with Slave Matrices) charge. Imagine facing down an army of even 20 such slaves - all of whom have charge body, mirror image, fire shield, air shield, invulnerability, etherial, quickness, ... who can be replaced at a cost of 10 Earth, 10 Astral, and either 20 gold (scouts) or a few gems (cheap commander summons, such as the Black Servant). Maybe they aren't full fledged SC's, but they would sure be effective as thugs. It would even be possible to get extra effects in there from the masters casting spells - one casts Astral shield, one casts Astral weapon, one casts Summon Earth Power (for the reinvig, not the +earth), one casts soul vortex, one casts Pheonix Pyre (for the kaboom if someone actually manages to kill one) - at a cost of one combat round for both the masters and the SuperScouts.
ugh. Nasty.

The SuperScouts could be placed in a row up front (they are cheap), the masters (one of which has a staff of storms to prevent an attack by fliers - beware Caleum! (sp?)) with bodygaurds - perhaps give the masters winged shoes for a faster retreat (maybe even give some of the masters slave matrices as well)