The Bride of Constant Vigil is the leader of the Shinobi Clan, one of the ninja clans to be forcefully allied with the Iron Dominion.  She originally sent her son, Espio the Chameleon, to Angel Island to observe Knuckles' activities as the Guardian of the Master Emerald, but since he exposed himself to the Chaotix, he had been "breaking taboo of his station."  As soon as the Iron Queen took over, she summoned Espio back to her clan to serve her.  However, once Sonic and the Freedom Fighters convinced her to break away from the Iron Dominion, she gave him permission to return to Angel Island with the others and do as he pleases.

Being that the Bride of Constant Vigil is Espio's mother with a calm personality, I want her to actually sound like a mother with a lower tone.  I guess you could say it should have a mysterious tone to it like Espio's does, but nothing too extreme.