What side is Severus Snape on?

Answer 1

Severus Snape joined the Death Eaters after he left Hogwarts. He was the one who overheard the prophecy and told Voldemort what he had heard. When Snape discovered who it was that Voldemort planned to kill he headed straight to Dumbledore to tell him and ask for her protection because he loved Lily (Evans) Potter.

Dumbledore said he would protect them but Snape had to do something for him and Snape agreed.

The plan was that Snape joined the Order of the Phoenix and remained a member of the Death Eaters. Voldemort thought he was in the Order to spy on them and give information to the Death Eaters.

In actual fact, Snape was a double, double agent. He worked for the Order telling them everything the Death Eaters knew and planned and told the Death Eaters only what Dumbledore allowed him to say.

Overall; he was an Order member.