Master Mode

Master mode is an option that can be selected during world creation, and can also be turned on through the difficulty slider in Journey mode. It further increases the difficulty of the game beyond Expert mode, offering Master mode-exclusive items. Like Expert mode, Master mode begins the moment the Master mode world is created, and cannot be altered after that by the player.

Enemies

 * All enemies deal more damage than in Expert mode.
 * All enemies have 50% more health than in Expert mode (therefore 3 times more health than in Classic Mode). For example, the Blue Slime has health instead of  or 25.

Player

 * Players will drop 100% of their Coins upon death instead of 50%.
 * Players gain an additional accessory slot that is only active while in a Master mode world. This stacks with using the Demon Heart, resulting in the maximum attainable slots to be 7.

Bosses
Bosses in Master mode drop a Relic, a statue resembling the boss. They can also drop a pet-summoning item which summons a pet that either resembles the boss or is closely themed after it.
 * Bosses in Master mode have increased health. Each boss has their own

Master-exclusive items

 * Bosses drop "Master mode" exclusive items similar to Expert mode, but they also drop their treasure bag, which contains the Expert mode items of the boss. They have a 100% chance to drop a Relic of themselves, and a 25% chance of dropping a pet, which is also modeled after themselves or is closely themed after.

Trivia

 * Master mode's descriptive text "Game over man, game over!", is a quote from the 1986 American science fiction action film Aliens.