Custom Artifacts
Oblivion has several categories and ways to obtain Custom Artifacts
Moonlight Artifacts can be obtained by gathering and combining a Moonlight Pentagram.

The combined 9 pentagram pieces first need to be collected, and then placed into the Moonlight Bag along with the other ingredients. Ingredients vary depending on the desired Moonlight Artifact.
Moonlight Bags can be purchased at any Mage NPC for 5725g.
Others:
Artifacts that require description:
Tokuno artifacts
balron sword
necrotyr items
poison dungeon items
Golden Chicken items (the ostard could be considered an artifact)
The dungeon in the island in ilsh items (golden horse bardings, golden horns, etc)
Any other item similar to the mentioned ones.
etc.