Snape, Rosier Sr & Various DEs In the initial ensuing madness of the battle, Snape joins other DEs in the Main Hall of Hogwarts and surprises them by attacking the eldest DE represented, The Elder Rosier, and saying enough that it's obvious he's a traitor. They are prevented from killing Snape by screams that indicate the students are gone, which sends them scampering through the castle instead and gives Snape time to disappear and begin looking for the Trio and/or Draco so he can assist them.