True Voice.
A passive infusion of World Law power into the tongue of a Higher Existence.
Artemisia had sometimes used it when she spoke to him urgently. No, it was more apt to say that it was Artemisia's 'natural' voice.
The normal voice she used to speak with him most of the time, was her making a conscious effort to withhold the power in her tongue so her voice only rang out in his ears.
But sometimes, she occasionally slipped back into her True Voice.
It was also because of this, that the Indirect Messaging Feature of the System existed.
[The goddess 'Artemisia' says …]
In cases like that, she was speaking with her True Voice, and the System was filtering out the power in her words and presenting it to him as a normal text message he could read.