Artifacts are special items that creatures will drop (In Dice & Tech Quests) if you happen to kill it with a critical attack, the Character that landed the Critical Deathblow, will get the artifact, Alternatively you can also gain the Hunter skill to get Artifacts more easily.
There are a toltal of 4 uses that an artifact has.
1. You can Sell it for Golji.
2. You can use it with the Invent Skill, to create an Item.
3. You can use it on your Summon.
4. You can use it on yourself, in the Lab, to learn Strand Abilities of other races.