Removes all current active curses on pickup, excluding Curse of the Labyrinth, and prevents all future curses (besides those created by Black Lantern) from appearing on entering a new floor.
All floors gain new curses unique to Black Lantern, that have both positive and negative effects:
Curse of the Imp: All Heart drops have a 50% chance to be transformed into Hollow Evil Friends, which deal 50% of Isaac's damage stat per tick and persist for 3 rooms before disappearing.
Curse of the Stone: Applies a carrying weight system on Isaac for the floor; holding no Trinkets or pocket consumables such as Cards or Pills grants a +0.45 speed up, while having more than 1 of these grant a -0.3 Speed down for each additional item.
Curse of the Sun: Grants a 10% increase to all stats for the floor, but taking damage replaces it with a -15% multiplier to all stats. Stat boost regenerates after clearing 3 rooms.
Curse of the Swine: All Coins will despawn after 2 seconds, but enemies now have a 50% chance to drop Coins on death.
Curse of the Ghost: Cursed ghost rain that hurts both Isaac and enemies alike pours down in rooms, indicated by crosshairs on the ground, and will increase in frequency the lower Isaac's health is. Enemies hit by the rain take 6.66 damage and are afflicted with fear for 4 seconds.
Curse of the Scythe: "Rage" builds when dealing damage, reaching max rage after landing 50 tears will trigger "rage mode" that halves Isaac's tear delay, but will also apply the Epidermolysis Pill effect, reducing Isaac's invincibility frames after taking damage. Rage mode lasts for 13 seconds.
Curse of the Master: Adds a "style" system for the floor that's influenced by Isaac's general performance, indicated by a glowing crown above Isaac's head; dealing damage will make the crown glow brighter, while taking damage makes the crown get dimmer. Depending on the brightness of the crown, all pickups and items are rerolled; higher "style" rank and a brighter crown grants higher quality pickups and items, while having lower rank and a dimmer crown reduces the quality.
Notes
Curse of the Swine will only have enemies spawned at the start of the room to drop coins; Additional enemies spawned by others can not drop coins when killed.
Curse of the Master's Style rank is calculated by a number between 0-100, and is divided into five tiers for pickups, and three tiers for items. The number starts at 50 at the beginning of the floor, and dealing damage to enemies will add about 10% of damage dealt to the Style rank, while Isaac taking damage will subtract 25 from it.
Pickup Reroll Quality:
Rank A — 90-100: Always upgrade.
Rank B — 70-89: 50% chance to upgrade.
Rank C — 31-69: Pickups are not rerolled.
Rank D — 11-30: 50% chance to downgrade.
Rank E — 0-10: Always downgrade.
Collectible Reroll Quality:
Rank A — 75-100: Items with an item quality < 2 are rerolled into items of higher quality.
Rank B — 26-74: Items are not rerolled.
Rank C — 0-25: Items with item quality > 2 are rerolled into items of lower quality.
Interactions
Black Candle: On pickup, resets and rerolls the current curse applied by Black Lantern of the floor — instead of removing Black Lantern's curses, grants a unique effect depending on the curse, removing or reducing their negative effects and retaining their positive effects:
Curse of the Imp: Friends now spawn in addition to Hearts instead of replacing them.
Curse of the Stone: No negative Speed penalty is granted for having high weight.
Curse of the Sun: No longer grants an all stats down after taking damage, instead simply removing the all stats up.
Curse of the Swine: Regular coin drops no longer timeout; enemies still drop temporary coins on death.
Curse of the Ghost: The cursed rain no longer harms Isaac.
Curse of the Scythe: No longer applies the Epidermolysis effect when reaching max rage.
Curse of the Master: No longer rerolls pickups and items into lower quality when having low style rank.
Video Showcase
Trivia
All unique curses granted by Black Lantern are references to various characters from popular The Binding of Isaac mods:
Curse of the Imp and Curse of the Stone are a reference to Fiend Folio's own two characters, Fiend and Golem.
Curse of the Swine and Curse of the Sun are a reference to a mod called Retribution, which featured two characters known as Mammon and Icarus, whose gimmicks were similar to said curses and even sharing similar names.
Curse of the Ghost is a reference to the character Mei, with the curse's effect being a reference to Tainted Mei's gimmick of producing raindrops to attack.
Curse of the Scythe is a reference to the character Samael.
Curse of the Master is a reference to the character Bertran and their own unique style meter.
Hidden in the spritesheet for Black Lantern's costume is a picture of Rumia from Touhou Koumakyou ~ the Embodiment of Scarlet Devil; and Touhou Bunkachou ~ Shoot the Bullet.
Rumia is a youkai with the ability to manipulate darkness.
Gallery
Curse icons that appear near the minimap for Black Lantern's own curses.
Easter egg found inside of Black Lantern's costume's spritesheet; Rumia from the Embodiment of Scarlet Devil.
Black Heart.
Hollow Evil Friends, which deal 50% of Isaac's damage stat per tick and persist for 3 rooms before disappearing.
Cards or 
Pills grants a +0.45 speed up, while having more than 1 of these grant a -0.3 Speed down for each additional item.
Coins will despawn after 2 seconds, but enemies now have a 50% chance to drop Coins on death.
Black Candle: On pickup, resets and rerolls the current curse applied by Black Lantern of the floor — instead of removing Black Lantern's curses, grants a unique effect depending on the curse, removing or reducing their negative effects and retaining their positive effects:
Fiend and 
Golem.
