Imaginary Place
Gain Entrance to Fenix Estate
Proceed up the courtyard here, taking care of any Locust you see on the way. I would be careful as these Drones around here seem to carry Lancers and will chainsaw you as quick as you try to get them.
The first wave will be two Drones and a Theron Guard. Once they are defeated another two Drones come and bring a Boomer along.
Once those two waves are clear, the third and final wave is another pair of Theron Guards. Clear them and the courtyard is secure.
Once you reach the estate, you'll come under fire and dive into cover. Once there the rest of the squad finds you and informs you of their situation. They found an APC and are working to repair it, while you and Dom clear the estate out and find what you're looking for.
Secure The House
As you enter the house, an Emergence Hole opens up on the right of the staircase. Toss it a well placed Frag Grenade to close it right up and take out whatever escaped.
Continue up the stairs, and clear out the three Drones that await you up there. Once the upstairs is clear, the building shakes as another Emergence Hole opens up below you somewhere. Head back downstairs now.
As you reach the bottom of the stairs, a Drone busts his way through a previously closed door. Make him wish he didn't, and take him out and continue through the door.
Follow through the corridor to find the Emergence Hole and the Drones it spit out. Clear a few out and the hole will close itself up.
Continue to search through the remaining rooms of the estate for ammo and other goodies, like the Cog Tag #27. You'll eventually find the closed off stairway that leads into the basement.