I'd been wondering for a while what exactly the Queen's witches, the Techeuns, actually looked like. From the grimoire:

The Techeuns' jewel-like augments flashed as they circled around her. Mara closed her eyes. A hum rose from the Techeuns, the notes fracturing into harmonies as, from the shadows, hundreds of tiny blue sparks burst to life before her.

Their appearance seemed somewhat bionic to me. 'Augments' comes up several times:

The Queen kept her expression carefully distant. She sat reclined in her throne, legs crossed, surveying the two figures at the base of the steps. Beside her, where the Wolves' Guard used to stand, Techeuns Shuro and Sedia hovered instead, their jewel-like augments gently humming.

In the gameplay trailer, I'd noticed some creepy peeps around the Queen (go to :43):

Now it looks like Bungie has confirmed these are the Techeuns. Not exactly what I was expecting. Via arstation:

Thanks to Xenos for keying me in to the new pic.

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Ha! I was reminded of these dudes:

Goddamn Mullins's shit is still the best.

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They fall on the "technology is magic" end of the spectrum and their augments are sleek and discreet. They look like a normal awoken with some "magic" swirling around and probably a 60 mhz whine. They probably hold onto many of the technological secrets of mankind's golden age.

Thematically, they are opposite the Warhammer 40K Mechanicum, who understand little and care even less about the aesthetics, only that the proper rites are observed.

However I bet both are secretive, scheming, and serious powerhouses with access to lots of lost technology a cut above what they give anyone else. I wonder if they operate the Harbingers?

and probably a 60 mhz whine

If an oscillation exists at over three decades above the typical cutoff frequency of human hearing, does it make a whine?

We just can't hear it. :p

He probably meant 60Hz.

B-b-b-basssss. 60hz is almost inaudible on the other end of the spectrum.

Definitely not a 'whine'

Maybe he meant 1600 hz. Not exactly pleasant, but definitely audible.