We've seen the Wraiths, Mirages, Subjectators, Guild Assassins, Indentured, Runners, Overseers, Zenith, Senteniels, Syndicate Colonizer, but we haven't seen the Syndicate Naval Unit.
Apparently they don't have naval units, since their vehicles float anyway
The vanguard were shown to have 11 buildable non-naval units in their spotlight video from a while ago. The same number of units has been shown for Dvar, but never at the same time I think.
Youtube
Judging from the various flavour texts, I'm guessing what it does it tap any latent psychic power of the user and convert that into some sort of effect.
So the user is the battery (or however psychic power works) and the PsiTec just removes the need for years to training for them to produce an effect, except that they need a different device for whatever effect they want to produce.
The faction spotlight described it as a channeling their personal pain as a weapon, so it's seemingly more in the first category.I'm not sure if the Tormented are actually experiencing agony, or remembering it. Their function seems to essentially be weaponising the collective memories of what was done to the Kir'ko and throwing them back at the humans that did it in the first place.
(Or, rather, their descendants)