Author's note
The original story is over and complete. Unfortunately English is not my mother tongue, so a long translation work is due. I'll split it in several chapters. Just be patient and don't flame too much. Thanks!

THE UNDYING LEGACY

Prologue

The great oak on the top of the hill quivered happily in the sunbeams' embrace. Blinking lights beaded its leafy brunches, wandering in the wind's whim. The mildest of June's afternoons, warm and cosy like a caress.
Some students lazily lingered on the lake shore, books open and eyes lost on the rippling water. Nobody seemed to notice the slender figure lying in the shadow of the stately tree, the right arm stretched under shiny hair, the left intent on grazing the humid and scented earth. All around an amazing bloom of lilies. As amazing as offseason. The white petals shone still despite the breeze, pale reflection of a countenance present, yet distant…

Annus horribilis

Hogwarts. The shape of the castle had always had something eerie, a sense of force without compromise, such as to bend the eyes and the arrogance of the boldest. But now the uneasiness had become ill omen. A sinister aura stifled the vital breath of the great building.
Iris Amberlin looked at the obsidian sky and wrapped herself tightly in her purple cloak. She could smell the rotten breath of the Dementors, but that was not an olfactory perception. Not sense, rather sensation. Chill besieging a heart still warm and vibrant and living. Two thin wrinkles rippled across her forehead. She wondered again why she was there, what she was looking for… She scanned every single stone of the castle, feeling more and more swallowed by its darkness.
The end of hope…
Then something changed. Her amber eyes darted to the tower that for years had kept the secrets of Dumbledore's white magic. A silver flash of light so brief and sudden to hover between the domains of reality and illusion.
She lowered her hood over the eyes, turning her steps towards the great entrance gates.
No, this is not the end…

'My dear child! We've been waiting for you quite a while. It's not safe to travel at night. Lately with Dementors and all the rest…' professor Sprout exclaimed, keeping cautiously low the tone of her voice.
'What do you mean with all the rest, Madame Sprout? Death Eaters? Lackeys of the Dark Lord?' her eyes like birds of prey over the headmaster's tower.
'For Merlin's sake! You don't realize the danger of…'
'…of granting the things the honour of their own names? On the contrary, professor. That's all but sign of lacking realization, ' a cold, deliberately slow voice wormed its way into the greenhouse.
'Good evening, headmaster,' Iris hissed, stressing with contempt the last word. She stood up to the black abyss of the man's stare, until he decided to break the time stopping spell.
'We meet again… at last. In all honesty I can't state I'm glad about it. Nevertheless, I understand the fascination Hogwarts can exert on those who have had the honour to…well, learn within its walls.'
Iris glared at the thin, bitter line those words had sprung from.
'I'm ready to take up the office you appointed me to, Sir. Starting from tomorrow, if necessary,' she replied without retaliating to the provocation.
Headmaster Severus Tobias Snape looked so intently at her that she feared to be dragged back into the old game of the legilimens cat and the mouse. She knew far too well the one sided rules of such a game… On a powerful instinct she emptied her mind and shielded her heart.
Now try it again, you bastard!
For a moment she thought she saw a sardonic smile creeping through the harsh features of the man.
'So be it,' he dryly replied and the way he had come -black, silent, unreadable- he left.
Professor Sprout stood open-mouthed, her eyes darting between the flapping headmaster's cloak and Iris' fierce look.
'Welcome back to Hogwarts, I suppose… Professor Amberlin,' was all she managed to say.