Wall of Flesh

"The master and core of the world..."

- The Wall of Flesh being summoned

The Wall of Flesh is the main antagonist and final boss the pre-Hardmode Terraria and the the secondary antagonist of Hardmode, behind the Moon Lord. It is, as it’s name implies, a gigantic wall of flesh with a set of razor sharp teeth and 2 eyes, unlike other bosses in pre-Hardmode Terraria, the Wall of Flesh can only be summoned by throwing the Guide Voodoo Doll into the lava of the Underworld while the Guide is alive.

Terraria
The Player must head to the Underworld and kill a Voodoo Demon to retrieve a Guide Voodoo Doll, the Player must make sure that the Guide is alive before they throw the Voodoo Doll into the lava, the Voodoo Doll must be thrown into the lava of the Underworld, if thrown into lava at any other location than the Wall of Flesh will not spawn, once the Guide Voodoo Doll is thrown into the lava, the Guide will die and the Wall of Flesh will be summoned off-screen.

The Wall of Flesh will then sweep at the Player's direction with its minions, The Hungry, all Players that are 1,800 feet away from the Wall of Flesh will be inflicted with the Horrified Debuff, all Players inflicted with it will be unable to leave the Underworld, if they try to leave or get behind the Wall of Flesh, they will get inflicted with The Tongue Debuff, where the Wall of Flesh sends a tendril to snatch the fleeing Player and forcefully put them into its mouth which deals 50 damage per second, the Player will not be able to move or use items while under the Debuff, if the Player attempts to escape by teleporting or running far ahead of the Wall of Flesh then leaving, the fleeing Player will instantly die with the message "(PlayerName) tried to escape.".

The more health that the Player depletes from the Wall of Flesh, the faster it moves, capable of reaching 50 MPH while under 500 health, if the Player(s) are unable to kill the Wall of Flesh before they get to the end of the Underworld, all Players in the Underworld will die and the Wall of Flesh will despawn.

It’s minions, The Hungry, are attached to long veins that are attacked to itself, they constantly and viciously attack the Player, the more the main body of the Wall of Flesh is attacked, the more The Hungry become resistant to damage and the more damage they do, once sufficient damage is done, The Hungry will detach and chase the Playwd, the Wall of Flesh's eye can fire lasers, the lasers become more powerful and more frequent the more damage the Wall of Flesh takes, sometimes the Wall of Flesh will "burp" Leeches which will then begin chasing the Player but will drop hearts upon death, the Wall of Flesh has 8,000 HP, the jaw has 50 ATK while the eyes have 22-30 ATK depending on the health of the Wall of Flesh, the jaw has 12 DEF while the eyes have 0 DEF.

On Expert Mode the fight with the Wall of Flesh becomes significantly harder, The Hungry now respawn as long as the Wall of Flesh is alive, the Wall of Flesh's, The Hungry's and the Leeches' stats have increased and the Leeches now only have a 20% chance of dropping a heart during the fight, the Wall of Flesh on Expert Mode has 11,200 HP, the jaw has 150 ATK while the eyes have 44-60 ATK, the jaw has 18 DEF while the eyes have 6 DEF.

Hardmode
Defeating the Wall of Flesh will make a status message appear saying "The ancient spirits of light and dark have been released.", then the entire world will change, the new Hollow biome is a available and the Corruption and Crimson biomes spread more quickly and new, more powerful enemies and bosses will come after the Player, and cool new weapons become accessible.

Trivia

 * One of the Cyborg's quotes are "Have you defeated the Wall of (GuideName)?", which is a reference to the Wall of Flesh being spawned when the Player sacrifices the Guide.
 * Some people see the Wall of Flesh as a god or deity due to its powerful and hard-to-defeat nature and because it somehow imprisoned the Ancient Spirits of Light and Dark, also defeating the Wall of Flesh causes the entire world/universe to reset, creating a new world/universe with more powerful enemies, bosses and weapons.
 * The Wall of Flesh being a god is even more plausible considering the fact that it can only be fought in the Underworld, a place ruled by the god Hades, and the Underworld is also called Hell in Terraria, which is ruled by Satan, someone who is believed to be similar or extremely close to a god.