In a Nutshell:
Master mode is the new ultimate difficulty. It offers little in new content and mostly changes stats and effects to increase the difficulty. Though the few items it does add are rewards for taking down the immensely difficult bosses and receiving all of them is well worth the pain if you’re ready for it.
The Journey’s End update brought many sweeping changes to Terraria. Wind now affects leaves and vines and falling particles, food items got an overhaul, and on top of them all, a new difficulty was added. Master mode, a difficulty option selected during world creation similar to Classic and Expert mode. It's the new ultimate challenge for Terraria players. Subtitled ‘Game over man, game over!’ in reference to the 1986 film Aliens, this mode is true to both its name and its motto. You must be a master to play this mode and if you aren’t, it's game over.
Being the difficulty above Expert mode, Master mode shares almost all effects with the old hardest difficulty. Bosses have their Expert mode AI and will still drop treasure bags with their Expert mode exclusive loot. Enemies will scale in health and damage as you progress through the game, getting buffs after the defeat of the Wall of Flesh and Plantera. Enemies have a higher chance to drop rare items as well as dropping more money. Enemies can still steal a dead player's coins by moving over them and will gain new attacks and debuff effects.
As mentioned before, enemies retain their changes from Expert mode but in Master mode they also receive another buff. All enemies get a three times multiplier to their health and damage as well as 20% more knockback. Compared to Expert mode, which buffs enemies by doubling health and damage and only increasing knockback by 10%.
Upon death, players now drop all of their money instead of 75% in Expert mode and 50% in Classic. Many debuffs inflicted on the player last longer.
To balance out the new difficulty players gain an extra accessory slot which will stack with the Demon Heart to give a new total amount of accessories being 7. On top of that defense is more effective than in Expert and Classic modes.
The biggest changes Master mode makes is its new items. These exclusive items have limited use and are mostly trophies for defeating the challenge of Master mode’s bosses. However some are mounts which prove to be incredibly useful in mobility.
From the King Slime
King Slime Relic - A placeable item depicting a gold figure of the King Slime. Reward for defeating the King Slime’s ultimate challenge.
Royal Delight - A pet item which, when equipped, summons a Slime Prince pet to follow the player.
From the Eye of Cthulhu
Eye of Cthulhu Relic - A placeable item depicting a gold figure of the Eye of Cthulhu. Reward for defeating the Eye of Cthulhu’s ultimate challenge.
Suspicious Grinning Eye - A pet item which, when equipped, summons a Suspicious Eye pet to hover beside the player.
From the Eater of Worlds
Eater of Worlds Relic - A placeable item depicting a gold figure of the Eater of Worlds. Reward for defeating the Eater of Worlds’ ultimate challenge.
Writhing Remains - A pet item which, when equipped, summons a Eater of Worms pet to float around the player.
From the Brain of Cthulhu
Brain of Cthulhu Relic - A placeable item depicting a gold figure of the Brain of Cthulhu. Reward for defeating the Brain of Cthulhu’s ultimate challenge.
Brain in a Jar - A pet item which, when equipped, summons a Spider Brain pet to follow the player.
From the Dark Mage
Dark Mage Relic - A placeable item depicting a gold figure of the Dark Mage. Reward for defeating the Dark Mage’s ultimate challenge.
Dark Mage’s Tome - A mount item which, when used, summons a Book Mount for the player to ride on. This mount will glide along the ground and allow the player to hover in the air after a jump.
From the Queen Bee
Queen Bee Relic - A placeable item depicting a gold figure of the Queen Bee. Reward for defeating the Queen Bee’s ultimate challenge.
Sparkling Honey - A pet item which, when equipped, summons a Honey Bee pet to hover around the player.
From Skeletron
Skeletron Relic - A placeable item depicting a gold figure of Skeletron. Reward for defeating Skeletron’s ultimate challenge.
Possessed Skull - A pet item which, when equipped, summons a Skeletron Jr. pet to hover around the player.
From the Wall of Flesh
Wall of Flesh Relic - A placeable item depicting a gold figure of the Wall of Flesh. Reward for defeating the Wall of Flesh’s ultimate challenge.
Goat Skull - A mount item which, when used, summons a Goat Mount for the player to ride on. This mount will behave identically to the Unicorn Mount.
From the Queen Slime
Queen Slime Relic - A placeable item depicting a gold figure of the Queen Slime. Reward for defeating the Queen Slime’s ultimate challenge.
Regal Delicacy - A pet item which, when equipped, summons a Slime Princess pet to follow the player.
From the Flying Dutchman
Flying Dutchman Relic - A placeable item depicting a gold figure of the Flying Dutchman. Reward for defeating the Flying Dutchman’s ultimate challenge.
The Black Spot - A mount item which, when used, summons a Pirate Ship Mount for the player to ride on. This mount will hover in the air and can move quickly horizontally.
From the Twins
Twins Relic - A placeable item depicting a gold figure of the Twins. Reward for defeating the Twins’s ultimate challenge.
Pair of Eyeballs - A pet item which, when equipped, summons the Raz and Spaz pets to hover beside the player.
From the Destroyer
Destroyer Relic - A placeable item depicting a gold figure of the Destroyer. Reward for defeating the Destroyer’s ultimate challenge.
Deactivated Probe - A pet item which, when equipped, summons a Destroyer-Lite pet to float around the player.
From Skeletron Prime
Skeletron Prime Relic - A placeable item depicting a gold figure of Skeletron Prime. Reward for defeating Skeletron Prime’s ultimate challenge.
Robotic Skull - A pet item which, when equipped, summons a Mini Prime pet to hover around the player.
From the Ogre
Ogre Relic - A placeable item depicting a gold figure of the Ogre. Reward for defeating the Ogre’s ultimate challenge.
Ogre’s Club - A pet item which, when equipped, summons a Baby Ogre pet to follow the player.
From Plantera
Pantera Relic - A placeable item depicting a gold figure of Pantera. Reward for defeating Pantera’s ultimate challenge.
Plantera Seedling - A pet item which, when equipped, summons a Plantera Seedling pet to follow the player.
From Mourning Wood
Mourning Wood Relic - A placeable item depicting a gold figure of a Mourning Wood. Reward for defeating Mourning Wood’s ultimate challenge.
Hexxed Branch - A mount item which, when used, summons a Tree Mount for the player to ride on. This mount will behave identically to the Unicorn mount but cannot double jump.
From the Pumpking
Pumpking Relic - A placeable item depicting a gold figure of the Pumpking. Reward for defeating the Pumpking’s ultimate challenge.
Pumpkin Scented Candle - A light pet item which, when equipped, summons a Jack ‘O Lantern pet to hover beside the player and emit light.
From Everscream
Everscream Relic - A placeable item depicting a gold figure of an Everscream. Reward for defeating Everscream’s ultimate challenge.
Shrub Star - A pet item which, when equipped, summons an Everscream Sapling pet to follow the player.
From Santa NK1
Santa NK1 Relic - A placeable item depicting a gold figure of a Santa NK1. Reward for defeating Santa NK1’s ultimate challenge.
Toy Tank - A mount item which, when used, summons a Santank Mount for the player to ride on. This mount will move quickly across the ground and fire a gatling gun and rocket launcher at enemies in front of it.
From the Ice Queen
Ice Queen Relic - A placeable item depicting a gold figure of the Ice Queen. Reward for defeating the Ice Queen’s ultimate challenge.
Frozen Crown - A pet item which, when equipped, summons an Ice Queen pet to hover above the player.
From the Empress of Light
Empress of Light Relic - A placeable item depicting a gold figure of the Empress of Light. Reward for defeating the Empress of Light’s ultimate challenge.
Jewel of Light - A light pet item which, when equipped, summons a Fairy Princess pet to hover above the player and emit light.
From the Golem
Golem Relic - A placeable item depicting a gold figure of the Golem. Reward for defeating the Golem’s ultimate challenge.
Guardian Golem - A light pet item which, when equipped, summons a Toy Golem pet to follow the player and emit light.
From Betsy
Betsy Relic - A placeable item depicting a gold figure of Betsy. Reward for defeating Betsy’s ultimate challenge.
Betsy’s Egg - A pet item which, when equipped, summons an Itsy Betsy pet to hover around the player.
From the Martian Saucer
Martian Saucer Relic - A placeable item depicting a gold figure of the Martian Saucer. Reward for defeating the Martian Saucer’s ultimate challenge.
Cosmic Skateboard - A pet item which, when equipped, summons an Alien Skater pet to follow the player.
From Duke Fishron
Duke Fishron Relic - A placeable item depicting a gold figure of Duke Fishron. Reward for defeating Duke Fishron’s ultimate challenge.
Pork of the Sea - A pet item which, when equipped, summons a Tiny Fishron pet to hover around the player.
From the Lunatic Cultist
Lunatic Cultist Relic - A placeable item depicting a gold figure of the Lunatic Cultist. Reward for defeating the Lunatic Cultist’s ultimate challenge.
Tablet Fragment - A pet item which, when equipped, summons a Phantasmal Dragon pet to float around the player.
From the Moon Lord
Moon Lord Relic - A placeable item depicting a gold figure of the Moon Lord. Reward for defeating the Moon Lord’s ultimate challenge.
Piece of Moon Squid - A pet item which, when equipped, summons a Moonling pet to hover around the player.
Master mode is no joke and it really should be a thought about choice to play it or not. It's important to note that Master mode has far less to offer when it comes to new content than Expert mode does, and the buffs it gives to enemies will make even slimes one or two shot your player throughout the entire game. It can be a grueling experience with little extra help to mitigate the difficulty. It should only be played by those who are truly ready and for those who are correct in their readiness will be rewarded not with items but with glory.
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