Vernon Terrell was the Adjudicator in Extremis for the Darkheart colony. He had not aged in the last three hundred years due to the effect of the Darkheart.
After Koschei had studied it, he gave rudimentary instructions on its use to Terrell, who used it to annihilate Terileptus. He was later shot and killed by Koschei. (PROSE: The Dark Path)