Delerenenard Sara Mathanith
This is his full name and darn it, it's how it's spelled no matter how many ways it's been spelled in all the different books.
Chancellor of the Eldritch Empire. Often mentioned, rarely discussed. Who is this man of mystery.
Delerenenard has the long face and clear, pale green eyes, both common in House Mathanith, where he has relatives. He is middle-aged (Liolesa's age or a little older), with creases around his eyes either from age or from stress.
(Checked Girl on Fire, Her Instruments, Major Pieces, and Jubilee Summer for "chancellor" ['cause I can spell that], and could not find a description of Delerenenard's voice.)
During the coup/insurrection, he guarded Bethsaida at the convent where she was sequestered. 
"The Chancellor's polished demeanor hid a ferocious intellect, as coolly wielded as a scalpel. There was humor there; Lisinthir suspected anyone who worked with Liolesa would need it, for she had a puckish streak." 
"If he was killing only your enemies, and willing to be directed by you, then he could serve as your weapon. But he picks his targets based on his own internal criteria, and it makes his actions too unpredictable." 
He has detailed knowledge of Liolesa's offworld endeavors, such as her research into the planet's and its people's fertility (or lack thereof).