Prerequisites: Rally Point Level 1, Main Building Level 3

At levels 10, 15 and 20 of the hero's mansion, you can occupy an abandoned valley (oasis) using your hero, allowing up to three oases per village. Depending on the annexed oasis, you will get an increase of production for a certain resource (or even two with some oases).

You can see the following details in the hero's mansion:

• Overview in each mansion about own conquered oases of the selected village
• Overview in each mansion about all conquerable oases of the selected village
• Overview of the production bonus provided by each oasis is shown
• The owner of all conquerable oases is shown in the mansion

The level dependent attributes (such as construction costs and generated culture points) can be found here.
For the full table of construction times click this link for server with 1x speed, this link for server with 2x speed and this link for server with 3x speed.