Main article: Bosses
The Wall of Flesh is summoned by throwing a Guide Voodoo Doll into a pool of lava or consuming it in the Underworld) while the Guide is alive. It is known by most players as the hardest pre-Hardmode boss, at 8,000 health (11,200 in Expert Mode), and defeating it will irreversibly enable Hardmode in that given world. Its defeat will also allow the creation of the summoning items for various Hardmode bosses. It can drop several powerful items, one of them being the guaranteed drop Pwnhammer which can be used to break Demon Altars or Crimson Altars in order to spawn various game-advancing Hardmode Ores, including: Cobalt or Palladium, Mythril or Orichalcum, and Adamantite or Titanium.
Upon summoning the Wall of Flesh, the player will be afflicted with the Horrified debuff, which prevents fleeing from the battle – any attempt to do so will result in severe damage via The Tongue or instant death if the player tries to teleport away. The Wall of Flesh will then sweep across the map, moving faster as its HP gets lower. It must be killed before it reaches the end of the map, otherwise it will despawn and any living players in the Underworld will die instantly. Additionally, the Wall of Flesh’s eyes fire lasers, the fire speed increasing as it is damaged, its mouth burps Leeches that will chase the player, and it has small mouths attached to it called The Hungry, which will also move toward and damage the player.
In Expert mode, The Hungry will rapidly respawn, and the Wall of Flesh will greatly increase its movement speed when it has 500 HP remaining, matching the full speed of Hermes Boots, so it is advised to wear the Lightning Boots while fighting him in expert mode. The Hungry that quickly respawn will seemingly block the wall from attacks and can deal quite a bit of damage themselves. The faster the Wall of Flesh moves and the quicker the The Hungry respawn, the more the player will have to focus on dealing damage and moving across a decent terrain. This can prove to be difficult to some players.