Once you gain support of all the three races available in the game, you can return to Mulandir. You can immediately go to the main quest and move to the next map. However, there are some side activities available here as well.
In the camp of each race you can find a commander or someone who takes care of the supplies for the faction. These people are: Flynn for humans, Eleon for elves, and Xarr for orcs (they are marked on the map as merchants). From each race you can buy plans that provide upgrades for your armies (for units of first and second level). These upgrades are expensive, but they enable you to increase the number of health points or to reduce the recruitment cost of units.
Additionally, if you completed quests 47 Blemishes, Star-Crossed Lovers and Zarach's Fang, you will also find blacksmiths in camps - Hegard, Vilron and Berghol the Bodacious. They can sell you weapons and army upgrades for elite level 3 units.
Conversations with companions
In Mulandir you can also talk to all characters who joined you (at this point they are Yria, Isgrimm, Gor, Ianna, Rohen and Uram - the first three can be found in Nexus and the rest are outside). This will enable you to learn more about the world and your companions. If you talked with Yria and Isgrimm before, now you will be able to continue the plot with them. Note: the conversations with companions are important - by learning their stories you unlock access to new abilities.
In order to continue the main plot you must go to Nexus and walk towards the table where you found the map during your previous visit. After agreeing on the plans you can use the world map to start one of two further missions.