As of 1.1.6 there are 17 possible artifacts that a player can discover during the course of their adventure. Each artifact is unique and only one copy of that item may exist in your save file. Each artifact has a red border to signify it's rarity. Should you wish to sell them they are worth over $700 each. It is possible to have multiple artifacts in your possession, but will require significant play time commitment to acquire just 2.
In order to gain the benefits provided by the artifact, you must equip it in the item slot. Whilst you may lose the option to wield a knife or use consumable items, the stat buffs provided are on par with a legendary item or better as some items unlock hard to acquire skills or perks.
Due to the low drop rate the list below has been mined from the game's data files. They are listed in the order they appear in the game's files. As some of the file names are in German, literal English translations have been applied, so their in game names may differ. Corrections to the names will be made when possible.
1) Secret Revelation to Moses: gain +5 Light Armour; Concentrate skill.
2) The Shield of Perseus: gain +5 Medium Armour; +2 Agility.
3) An Archaic Figurine: Gain +1 Agility, +1 Bravery.
4) The Book of the Dead: gain damage vs Undead, Forbidden Lore Specialisation.
5) The Sword of the Cherubim: gain +1 Dexterity, +1 Reflexes, +1 Endurance.
8) Emerald Scarab: 10% Reduction in damage received, gain Vanish skill. Shown in the codex. Listed in the files as Smaragd, which is an archaic term for emerald. Red emeralds do exist, but they are rare.
10) The Travel journal of Herodot: gain +1 Endurance and the Survivalist specialisation. Listed as Reisebericht Herodot in files.
13) Rabbi's Staff: gain +1 agility and Sixth sense specialisation. Listed as Gehstock Rabbi in files.
14) Deployment Plans: gain a damage to Nazi's buff. Listed as Aufmarschplaene in files.
17) Petru's Amulet: gain +4? to reflexes and a damage to Cultists buff.