Hogwarts' Professor of Dimensional Studies

Robin arrives in the world of Harry Potter, in the same year as Dumbledore, and activates the DNF Magic World System.

After changing class to Dimension Walker, a hundred years later (more or less)... a new professor of dimensional studies arrives at Hogwarts.

Dumbledore: "Now I can raise The Chosen One without a worry!"

Voldemort: "Avada Kedavra! ...Why won't you die either?!"

Harry Potter: "He's the best professor at Hogwarts!"

Robin: "Well said. Fifty points to Gryffindor!"