Wall of Steel

The Wall of Steel is a boss that can be spawned in the Underworld by letting a Mechanical Guide Doll fall into lava after Hardmode has been unlocked. It is a stronger, mechanical version of the Wall of Flesh. Once the doll has fallen into lava, the Guide will die, and the Wall of Steel will awaken.

Battle
Like the Wall of Flesh, the Wall of Steel has a mouth and two eyes. The eyes must be shot at first. Once they die, Probes and The Hungry will stop spawning out of the mouth. Before the eyes' death, the rest of the body is indestructible. When the eyes die, the mouth will start breathing fire at the player. The rest of the body will be covered with spines that inflict damage to any player that attacks it with a melee attack. The eyes each have 4,000 health and the mouth has 6,000. Once the mouth dies, the entire body will begin moving faster and also be open to attack. It has 10,000 health. Once the body is destroyed, the drops from the Wall of Steel will be spawned inside a square of Demonite Bricks.

After the defeat of the Wall of Steel, a message will appear stating "The ancient spirits of light and dark have come to wage war!" This marks the beginning of War Mode. Three types of ore will also spawn: Cryocite Ore in the Snow biome, Verdantite Ore in the Jungle and Aridite Ore in the Desert.

Drops
Only one of the following will drop
 * Coins
 * Greater Healing Potions
 * Crimson Emblem (Only if the world has Crimson)
 * Corruption Emblem (Only if the world has Corruption)
 * 10-20 Souls of Fight
 * War Pickaxe (12.5%)
 * Sun Waraxe (12.5%)
 * Shadow Blade (12.5%)
 * Steel Gun (12.5%)