Lucas began outlining the film around August 1977, introducing ideas such as the Emperor and the notion that Luke Skywalker had a long-lost sister. Lucas also started considering ways to explain Luke actor Mark Hamill's facial scars (which he suffered in a January 1977 automobile crash) within the context of the "Star Wars" universe. According to Hamill, Lucas told him that, had Hamill died in the accident, he would have replaced Luke with a new character. This led to the creation of the Wampa, a monster that dwelled on the planet Hoth that mauls Luke in the opening scenes of the film. Story conferences began on November 28, 1977, after Lucas hired Brackett. The two held story conferences until early December, and Brackett wrote her draft while McQuarrie began to paint concept art. Lucas and Brackett discussed including the planet of the Wookiees (which had been considered for the first film), a new alien species, and two new characters—the Emperor and a gambler from Han Solo's past. Lucas also decided early on that they needed to introduce a new teacher for Luke, since Obi-Wan had been killed off in the first film.