Minecraft wiki entry for Advancement_guide, associated text: The first step is building the biggest nether portal possible (23x23). Before attempting to move the ghast through it you should enter the portal to load the chunks and remove any block which might suffocate the ghast. Then you can use fishing rods (prepare a lot of them because they break really fast) to move a ghast through the portal. Keep a flint and steel in the hotbar in case the ghast breaks the portal. Elytra and fire resistance potions are not necessary but really helpful.