Millennium Items
Millennium Puzzle: Home to the ancient Pharaoh who sealed away the shadow games. It's powers remain largely unknown. It does give Yami several abilities such as mindcrush and the ability to 'purify' minds by removing evil from them. It can also undo some of the magic of other items. For example, when Bakura used the millennium ring to place Ryou's soul in a card Yami switched their places.
Owner: Yugi Moto
Spirit: Yami, the ancient Pharaoh
Millennium Ring: Home of the ancient thief Bakura (?). The ring can steal souls it also acts as a sort of compass, locating other millennium items. Using it Bakura can summon things from the shadow realm into our world, or send things from our world to the shadow realm.
Owner:
Bakura Ryou (later given to Yugi, but then Yami Bakura steals it back).
Spirit: Bakura, the ancient thief
Millennium Eye: This eye can cause madness in those not destined to possess it. It posses the power to read minds and to steal souls.
Owner:
Maximillion Pegasus, Bakura Ryou (later)
Millennium Rod: This item has the power to control others' minds.
Owner: Marik Ishtar (in ancient times it belonged to the High Priest who looks like Seto. At one point the item helps Seto indicating that it actually is his), eventually given to Yugi.
Spirit: None - Many people believe Yami Marik to be the spirit of the rod, however, Yami Marik is actually a creation/manifestation of Marik's hatred and therefore not a millennium spirit. This would make sense since the rod belonged to Kaiba in the ancient past. If it had a spirit it should be Yami Seto, not Yami Marik. Yami means dark, so Yami Marik is still a yami even though he is not a spirit.
Millennium Necklace: This item can see into both the future and the past, but be warned, the future is forever changing.
Owner:
Ishizu Ishtar, eventually given to Yugi.
Millennium Key: This item allows the owner to 'walk the corridors' of another's mind. That is, to freely search all aspects of another. The eye only allows for specific thoughts or reactions not personality etc.
Owner:
Shadi
Millennium Scales: This item apparently gives the owner the ability to judge between truth and lies, good and evil. If it judges one false it also punishes.
Owner:
Shadi