From being cleared of the Ministry of Magic's bounty and wanted notice for murdering Dumbledore due to a lack of concrete evidence, to being appointed Headmaster of Hogwarts by the School Board, Snape had remained remarkably indifferent throughout, as though it were all perfectly natural.
When he returned to Hogwarts, he ignored Hagrid's murderous glare, passed through the castle's oak door, and headed straight for the Headmaster's Office. During the short walk, Snape could feel the hateful stares of his former colleagues. Though they were all careful to conceal the anger and hatred in their hearts, Snape knew they did not welcome him. They even wanted to kill him to avenge Dumbledore.
Yet laughably, he had only done as Dumbledore instructed.
"As you wished, I have returned and become the most unwelcome person here!"
After entering the Headmaster's Office, Snape approached the portrait of the former headmaster and spoke in a faintly mocking tone.
"Hogwarts has now completely fallen into Voldemort's hands." The sleeping old man opened his eyes, looked at his successor, and said calmly, "I hope you can fulfill the vow you once made and do everything in your power to protect Hogwarts' students."
"That won't be easy." Snape's lips twitched as he said softly, "The Dark Lord demands that I expel all Muggle-born students. You know I have very little power to choose otherwise."
After a brief silence, Dumbledore smiled. "That was to be expected, wasn't it? Just like Salazar Slytherin, they are prejudiced against Muggle-born wizards and wish to drive them out of Hogwarts."
"The situation is even worse than you imagined."
Snape could not understand Dumbledore's composure. He pulled out a newspaper from several days ago from his robe pocket. "Perhaps you aren't aware that the Ministry of Magic now has a Muggle-Born Registration Committee.