The Lamp of Dark Obstruction is used against the Genie, temporarily blinding the boss. It's also known as just the Magic Lamp. It is found in the Erupting Fissure which can be found in the Ice Domain.
Information is unknown because the Ice Domain and Desert Realm are in different consoles. PS2/N64 has the Ice Domain and Arcade/Dreamcast has the Desert Realm.
It's found in the Ice Domain in the level Erupting Fissure.