Here are the grades of Artifact.
Mortal grade: This is a normal artifact used which does not posess spiritual energy but can be slightly infused with one.
Spirit Grade: This is an artifact which possess spiritual energy usually used by Qi-refining to Core formation cultivators. It is divided into Low, Mid, High and Peak grade.
Treasure Grade: This is an artifact created with the aid of beast cores. It is divided into Low, Mid, High and Peak grade.
Immortal grade: This is an artifact normally created by immortals or using rare materials or with the aid of rare occurrence. It is divided into Low, Mid, High and peak grade.
Supreme grade: This is an artifact from the Ancient era, primodial realm or forged by Gods