Expert Mode

"Fortune & Glory, Kid."

Expert Mode is an option that can be selected during world creation. It greatly increases the difficulty of the game, while providing the player with many opportunities to gain powerful items exclusive to Expert Mode.

Enemies
Bosses are harder to spawn
 * Enemies have 2x more health and do 2x more damage. (Doubles when spawning the monster, before taking defense into account)
 * Enemies and bosses in that particular world have more difficult AIs.
 * Weaker enemies gain increased stats as the players progress, starting in hardmode.
 * Monsters have a small chance to spawn in towns, although they won't spawn in front of background walls.
 * When attacking enemies for too long, there is a chance that more of the same enemy will spawn close by and join the fight (e.g. attacking 1 Umbrella Slime causes more to spawn and attack.)
 * Ice Monsters have an additional chance to freeze the player upon a successful hit on the player.
 * Many enemies gain additional attacks.
 * Bats have a chance to give the Feral Bite debuff, increasing player damage but lowering health regeneration. This debuff will also cause other random debuffs to be applied to the player.
 * Some zombies carry an arm, causing them to have an extended range and higher damage.
 * Spiked Slimes can shoot up to 6 spikes at once.
 * Some skeletons can throw bones.
 * Lava Slimes drop a puddle of lava when killed.
 * Jellyfish gain a new shock attack in which they move in a straight line and take no damage.

Bosses

 * Each boss offers a unique Expert Mode item when defeated, contained in Treasure Bags they each drop. These items were originally only exclusive to an expert mode world, but were eventually retracted so that all but one endgame item (the Demon Heart, which grants a sixth accessory slot) can be used outside of Expert Mode.
 * Bosses have more health.
 * Some bosses gain new, more difficult attack patterns.
 * Boss health scales in multiplayer depending on the number of players.

Loot

 * Enemies drop more loot, including higher percentage chances (usually doubled chances) to drop certain items.
 * Pots now drop more stuff when broken.
 * Fishing quest rewards give more money.
 * Developer items are obtainable and will not kill the player when worn. (Because of this, Red's Wings no longer have their unique attributes.)

Player

 * Life Regen isn’t as effective unless the player has the Well Fed buff. (Your Life Regen is debuffed when you are in expert mode and not Well Fed)
 * Vampire and Spectre healing is slightly less effective than in normal mode.
 * The Defense stat grants 75% damage reduction instead of the 50% it gives in Normal mode. However, it is still less effective because enemy damage is multiplied by 2 while damage reduction is only multiplied by 1.5, and as a result you will take more than twice as much damage from enemies given the same amount of defense. For example, let's say you have full melee Adamantite armor (50 defense) with no other defense bonuses and get hit by a Giant Bat (45 damage in Normal mode). In Normal mode, you get 25 damage reduction from 45 damage and take 20 damage. In Expert mode, you get 38 damage reduction from 90 damage and take 52 damage.
 * Entering water in the Snow Biome causes the Chilled debuff for about 5 seconds. The debuff takes effect infinitely if the player does not exit the water.

Death

 * You drop 75% of your gold upon death.
 * Enemies can pick up your dropped coins when you die. Kill them when you respawn to get your coins back. Enemies holding dropped coins emit a sparkle effect based on the color of the best coin they're holding. There is a chance that if the enemy you killed is far away enough from your spawnpoint or another player, it will despawn, taking the coins with them.
 * Respawn times are increased to 30 seconds during boss fights.

Expert-exclusive items
Expert Mode-exclusive items are found inside Treasure Bags, dropped by bosses, and have the Rainbow rarity. While these items can only be obtained via an expert mode world, they still function in regular worlds, excluding the Demon Heart.

History
Bosses now drop special Expert-Mode-only items.

Mode Expert Expert Mode