Mrs. Black stood at the window, looking out into the garden behind her home, Kreacher kneeling subservient on the floor behind her, "Tea, Kreacher." She demanded in a cold and emotionless voice.
"Kreacher wishes only to serve his Mistress." He said, his voice slicked with the devotion of ages spent serving the only woman he'd ever respected. She was everything in his world and he would never leave her, had he the choice.
She heard the vermin of an elf skitter from the room, his low voice grating on her nerves as she watched for the owl she knew would be coming. Regulus had promised her a gift in his last letter, something worthy of her, something deserving of a Black. Regulus would never disappoint her, had never disappointed her.
The cup of tea clattered against its saucer as Kreacher returned with the tray of tea and biscuits, "Will Mistress take her tea at the window again?"
She nodded carelessly, "Yes, Kreacher."
He placed the tea tray carefully on the floor before running for a small table, dragging it over, and placing the tray on its top.
Mrs. Black never once looked up, her eyes trained on the garden hedge. She reached out and grasped the saucer, lifting it under her nose to inhale the scent of her afternoon indulgence. Strong and black with honey and no cream. Always the same and exactly the way she liked it. She lifted the cup to her lips and sipped the sweet liquid into her mouth, letting the taste of honey and oolong seep into her tongue, scalding the inside of her mouth. She never flinched.
Kreacher bowed and ran out of the room, leaving his Mistress in peace. He would dust the grand piano in the Music Room again. Everything must remain tidy for his Mistress. She desired order and Kreacher lived to serve.
A speck appeared on the horizon, flying slowly toward the window. She still did not move, blinking rarely and continuing to drink her tea. The oolong seared itself into her tongue, forcing her to feel something again, even if it was only heat and pain.
She sipped the tea down to the dregs, swirling it around in her hand a few times as she watched the speck grow ever larger. The owl, a large, beautiful eagle owl landed on the sill just as she returned the empty teacup back to the saucer, face down.
She silently reached out to the owl, taking the small package from it. She peeled back the brown paper to find a note and a small velvet box.
Mother,
I promised you something grand and worthy of a Black. Please take this as a sign of my affection for you. Cherish it and never lose it.
I will do my duty by the Dark Lord and the name of Black will be spoken again with the reverence it deserves.
Your Dutiful Son,
Regulus Black
She lifted the top of velvet box, a smile twisting across her usually stern face. Regulus had done well. She lifted the bauble from its place in the box and delicately put it on, turning to a nearby looking glass, enjoying the effect of the metal against her pale skin. She would never wear the ornament again, it was too valuable, but just this once she enjoyed feeling its weight.
Kreacher returned half an hour later to see his Mistress still admiring her reflection in the glass. He picked up the tea cup and moved it from its place upside down on the saucer so as not to break it on his way out, "Mistress looks very regal in her new jewellery."
She reached up, the austere look gracing her refined features once more. She removed the trinket and placed it on Kreacher's tray, "Lock that into the Drawing Room cabinet with the rest of the heirlooms."
He nodded and backed away from her, "Kreacher will do his Mistress' bidding. Kreacher will make sure the snake locket is safe in the cabinet before he washes the tea dishes." He walked out of the bedroom once more. The biscuits remained untouched; the locket lay heavily against the tea cup; and a crookedly formed cross seemed to shout trouble at the house elf from the dregs in his Mistress' saucer. But Kreacher only saw jewellery and yet more dirty dishes.
A/N: This is my own interpretation of who R.A.B. is and where the locket is now. Go ahead and look in Book Five in that cabinet in the Drawing Room. There was a heavy locket there until the Cleaning Crew emptied it out!