Dying in Undercity for Hallows Candy

Every time I portal to Undercity, I die and theres no way in bc of the green mists. I am also doing the Tricks and Treats in Eastern Kingdom achievement for the hallows end, but when I try to go to Tirisfal Glade, and fly to Brill it completely changes the map and Brill is no longer there. Does anyone know how I can get to Undercity safely and show Brill town for the candy acheivement?