Minecraft wiki entry for Combat, associated text: Ghasts are often considered the most difficult mob to kill in the Nether because of their extreme attack range, explosive attack power, mobility, and flight. Players in any exposed area will have to deal with them sooner or later and possibly from the moment they step out of a portal. Ghast fireballs have a profound effect on nether architecture, making a compelling case to use only materials resistant to their explosions for outer walls and exterior fittings in places where their attacks may be drawn. As a result of their large size and the extreme unpleasantness of an indoor ghast spawn, the primary defense mechanism for buildings in the Nether becomes enclosure. A ghast's firepower is highly inaccurate at most ranges if one is moving. Players are most vulnerable when they are building in the Nether, when they may not be moving and possibly standing above a long fall. Ghasts can also break blocks from under the player, often dropping them into lava or causing death through fall damage.