To reach Catherby, you can use several methods. If you have completed the Camelot teleport quest, you can use the Camelot teleport spell to teleport directly to Camelot and then run south to Catherby. Alternatively, you can use the Ardougne teleport spell, which will bring you close to Catherby, and then travel eastward. Additionally, you can use the Catherby lodestone if you have unlocked it.