That Omega Feeling (слэш)

His breath came fast and shallow.
This isn’t a fever.
“Potter!” Snape barked.
Harry’s head swam. His skin prickled. Then came the flush, flooding his cheeks, trailing down his spine, settling in his core.
Oh, shit.
He looked up, eyes wide.
Snape was staring back, and his eyes… they weren’t human anymore. They were black, blown wide with instinct. Alpha instinct.
Everything snapped into place like a trap closing.
Because of course he wasn’t a bloody, mundane Beta.
He was maturing—late, but unmistakably—into an Omega.