Most common items in the game
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Amethyst Necklace - Contact damage when invincible
Armor - +20% damage reduction
Attack Speed Tonic - +20% attack speed
Better Pot - Only large potions drop from pots
Bigger Map - Reveals the entire map
Blue Book - Mana regen decreased by 50%
Blue Cloak - Occasionally fires 4 projectiles when hit
Blue Crown - Mana potions also heal health
Blue Mushroom - Regen mana while attacking
Credit Card - Can go 500 into debt
Critical Chance Tonic - +10% crit chance
Debit Card - Every unexplored shop has 1 free item
Diamond Necklace - Doubles invincibility time
Emerald Necklace - Decreases roll cooldown
Eyeglasses - +15% crit chance
Flame Boots - Increases speed when invincible
Flowered Boots - Afflicts poison to enemies when touching them while invincible
Gas Mask - Immunity to root
Gold Bag - +1 coin to every coin collected
Golden Bag - Holds +2 weapons (does not stack with Leather Bag)
Golden Chest - Increases amount of coins from small chests
Gray Cloak - Enemies do not attack until attacked
Green Book - Recover mana upon taking damage
Health Flower - Recover health when killing an enemy
Health Tonic - +20 health
Honey Pot - Potions grant brief invincibility
Horseshoe - Doubles enemy drop rates
Informative Map - Shows nearby structures on the map
Knight's Shield - 20% to dodge damage
Leather Bag - Holds +1 weapon (does not stack with Golden Bag)
Magic Gloves - Increases mana regen proportional to max mana
Magnet - Increases coin and potion pickup range
Mana Flower - Recover mana upon killing an enemy
Mana Ring - Recover mana upon hitting enemies
Mana Tonic - +20 mana
Medic Flask - Immunity to poison
Money Bag - If below 500 coins, sets coin count to 500. If above 500 coins, double coins. If in debt, set coin count to 0.
Reach Arrow - Increases range of melee weapons and increases projectile velocity
Red Crown - Health potions restore mana
Red Mushroom - +25% damage when invincible
Ruby Necklace - Double health from potions
Running Shoes - Increases roll distance
Sapphire Necklace - Double mana from potions
Speed Boots - Invincible rolls
Speed Tonic - +4 speed
Spiked Armor - 60% chance to damage enemy that hit you
Topaz Necklace - Lowers stun from being hit
Vest Explosion Proof (yes, really) - Immunity to explosions (like Canta's presents)
Zumbi Headphones - Immunity to slow
Zumbi Scarf - -20% mana cost

Rare and strong items, though with a downside. Best utilized by Cotaka
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Bombrella - Summons many bombs upon entering unexplored rooms, damaging everything
Casinos' Dice - Randomly raises or lowers damage, attack speed, crit chance, knockback, and mana cost by 5%.
Cursed Book - +20% attack speed, -40% health
Double-Edged Sword - +30% damage, -20% damage reduction
Paper - +20% attack speed, -30% crit chance
Scissors - +30% crit chance, -30% damage
Stone - 30% damage reduction, -15% attack speed
Sword Handle - Greatly increases range of melee and projectile velocity, -10% attack speed
The Curse - +20% to damage, attack speed, crit chance, knockback, and mana cost but -20% to health, mana, and damage reduction

Even rarer than cursed items, they boost stats majorly without any downsides. Some characters come equipped with ultra rare items such as Cotaka with White Book or Ducky with Medic Syringe
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4-Leaf Clover - 20% for double items in big chests
Blue Star - Crits do x3 damage
Canta's Power - (exclusive to Canta) +2 max health and mana every room clear
Magic Mirror - Replaces rolls with a smoke dash, players disappear until end of the dash
Medic Syringe - (Ducky starts with this) Immunity to all debuffs
Piñata - +20% chance to find ultra rares in shops and big chests
Red Book - Increases damage proportional to health remaining
Skull - Stats cannot be lowered past 0%
The End - Dropped by Hactus, ends the game upon pickup
The Item - +10% to damage, attack speed, crit chance, knockback, and mana cost
Voodoo Doll - Grants second life. Player is invincible while health regenerates after dying
White Book - (Cotaka starts with this) Immunity to all curses (like Skull, but better)
Zeke's Band - Dropped by Zeke occasionally, +10% damage, attack speed, and crit chance

Small category of items. Pets provide a bonus upon specific conditions and orbit the player.
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Little Knight - 20% chance to trigger +30% attack speed for 4 seconds when hit. Boost is indicated when the knight turns red
Little Witch - When health is below 30%, -30% to mana cost. Boost is indicated when the witch turns blue

Thanks for stopping by and reading my guide. Maybe eventually I'll make a weapon guide later but this is all for now. Farewell :3

Also thanks to KaboinkC and Exist3nce (will add as contributor soon). Initially this guide was something me and the boys compiled on Discord but I felt like sharing it here too.