This will probably be unlocked in normal play and you'll need any 23 of this list:
Clover
The Map
Powder
Totemus
Heart Amulet
Guitar Hero
Magic Mushroom
Economicon
Magic Ring
The Blood Tooth
The Candle
Dice
Hourglass
Boomerang
Holy Grail
Hermes Boots
Bottle of Death
Holy Shield
Mjolnir
Gamepad
Kunai
Lager
Glasses of Dwarf
Alchemicon
Medallion
FisherMan
Coupon
The Elder Helmet
Dynamite
Diamond Pickaxe
Crying Baby
Helmet of Miner
The Golden Hearth
The Golden Tooth
The Blue Tooth
Ring of Ci8
Lockpick
Cross
Candlevania
Pact
Pact 2.0
Spurs
Cloud in a jar
Emerald
Bob
When you have enough, you'll need to view your artifacts page in the "depository" on the main menu to get the achievement to pop. Artifacts that a class starts with do not contribute to the achievement, you must find them with a different class.