The "Blood of the Daedra" quest in The Elder Scrolls IV: Oblivion requires the player to obtain any Daedric Artifact and give it to Martin Septim for a ritual to open the gate to Camoran's Paradise. There is no single specific artifact required; instead, any one of the 15 Daedric Artifacts found in the game can be used. Some notable points about these artifacts and the quest:

• The artifact given to Martin will be permanently lost for the remainder of the playthrough.
• Players are advised to choose an artifact they feel least attached to or not crucial for their gameplay going forward.
• Azura's Star is a commonly obtained artifact early on, but players often prefer not to sacrifice it due to its reusable soul gem power.
• Other suggested artifacts to give include the Saviour's Hide or Namira's Ring, as these may be less essential or obtainable later in the game.
• Any Daedric Artifact will fulfill the quest requirement and allow progress in the main story.

In summary, the quest does not specify a single artifact; any one of the Daedric Artifacts found in Oblivion can be given to complete the "Blood of the Daedra" quest.