Old Blood: Missing Scout
This mission can be initiated by speaking to the Chief Scout in Tuchanka and speaking to him about a missing scout prior to heading out on Mordin’s loyalty mission ‘Old Blood’.
During the mission, you will eventually come across a sick Krogan. Convince him to return to the Urdnot Camp to complete the mission. You can see the walkthrough page for the exact details.
This mission can be initiated by picking up the Combustion Manifold item from a flipped vehicle in Mordin’s loyalty mission - Mordin: Old Blood (see the walkthrough page for the exact location).
To complete the mission, you will need to turn in the Combustion Manifold to the mechanic working on the APC near the Krogan clinic after completing the Old Blood mission. Doing so will complete the task.
Find the merchant Ratch on Tuchanka and enter into a conversation with him. Push the dialogue towards talking about Pyjaks. After a few lines, you’ll receive a side-quest to eliminate some of the critters.
Run over to the turret by the Chief Scout nearby and interact with it. This will initiate a short mini game that has you shooting at waves of Pyjaks that run across the open ground towards your position. You need to eliminate three waves of these with fewer than five escaping in order to complete the task.
Once successful, return to Ratch and speak with him to end the side-mission.