Severus Snape miraculously lived from Nagini's bite on his neck. Story takes from there at end of the Battle of Hogwarts. [CHARACTERS ARE THE CREATION OF J. K. ROWLING. STORY IS MY OWN TWIST SO, SPOILERS MAY APPEAR. DON'T READ UNLESS WANT TO READ THEM.]
Chapter 1: Shriek of panic.
Severus Snape opens his eyes, he is lying on floor of the shrieking shack. He looks at his neck to see he is still bleeding and so still alive.
He rolls up his left sleeve to check his watch.
It says 10:30pm.
I was dead a half an hour?
A bloody half hour and I am alive.
How is that possible?
Snape recollects the last things that happened to him.
POTTER! The memories… He saw but did the Dark Lord kill him?
Snape got up off the ground and took out a potion vial from his robe pocket of Essence of Dittany.
He uncorked the vial and drank it.
With a grimace, Snape swallowed and after 5 minutes saw the wound in his neck disappear.
That's done but, what the bloody hell do I do now? Should I go find Potter? But where do I look? The pensive! Could he still be in there watching the memories? Just bloody great I got to go look for Potter all around the damn ruddy castle. Merlin this is bloody annoying.
Putting on a disillusion charm, Snape walked out of the shack and flew to the school.
He looked from the Great Hall, his former offices', to the Room of Requirement, which was burning of what looked like fiendfyre to him and tried to put out but failed and had to run out of there.
Snape thought of where else to look and could think of nowhere and then, it dawned on him.
The Forbidden Forest!
Snape, running as fast he could ran in the forest just as he saw Harry on the ground and saw Rubeus Hagrid pick him up.
He's dead…!
While he watches and silent and hidden walks with Hagrid he hears him talk:
"Are y'eh happy now? Are y'eh that Harry Potter's dead?" and as they walked into the Great Hall and everyone (-Snape saw-) was watching Voldemort walk in with Hagrid and the Death Eaters behind him.
They stopped when they all were in there and everyone watched Voldemort speak:
"HARRY POTTER IS DEAD!"
A panicked shriek filled the halls and everyone turned to see Ginny Weasley shriek again and then faint.