Artifacts are items you can equip to any character to boost their skills in a particular way. There are 3 Artifacts slots that are shared across all characters and each offers their own set of buffs that can be upgraded up to level 3.
All Artifacts are earned naturally as you play.
Each game you play will give you a bit of progress towards earning another Artifact. You can check your progress under the Competitors tab > Select any character > Artifacts.
You don't need to level them up to unlock this achievement.