Professor Prince and the Half Blood Prince

Severus Snape is given the chance to relive his life once more but this time not as his teenage self but as his snarky professor self. Severus decides to go back in order to mentor and guide Slytherin House away from Voldemort. Opens at the start of Severus's the younger's Fourth Year at Hogwarts. Slow-burn SSLE. MentorSeverus! FatherlyDumbledore! SanerVoldemort? Slytherincentric!