A researcher needs the Obelisk of Karza to help with the Crucible project. Recover it from the Hades Nexus and deliver it to him in the Presidium Commons.
Alternative journal entry:
The Obelisk of Karza was recovered from the Hades Nexus. Find someone on the Citadel who can use it.
Acquisition[]
After the Cerberus attack on the Citadel, listen to the researcher with a datapad sitting at the Courtyard in Presidium Commons, talking to someone on comms. He is on a bench near the billboard for Meridian Place, to the far right from General Septimus Oraka's bench. His team apparently ran out of time digging for the obelisk, and now it's in off-limits territory.
Alternatively, the obelisk can be found during a routine Search and Rescue operation once the Hades Nexus becomes accessible after the resolution of the geth-quarian war. If the object was retrieved in this manner, the mission initially appears in the journal as Citadel: Obelisk of Karza and later updates to the present form once you overhear the researcher talking about it.
Walkthrough[]
Scan the moon Kopis from the Hoplos system in the Hades Nexus cluster and speak to the researcher when you return to the Citadel. The obelisk is an artifact containing Prothean language translations, apparently akin to the Rosetta Stone but for Protheans.
After handing over the artifact, you will gain 5 Reputation, 15,000 credits and an update to the Alliance Engineering Corps War Asset.