Portals allow to significantly reduce the march time to a selected location. They basically act like a shortcut to your city. In order to open a portal, click any location on the world map and select the “Open Portal” option. You cannot open portals on the territory of any clan other than your own. You also cannot open portals to other Kingdoms outside the Kingdom Clash. Note that in order to open portals, you need to build the Portal Master in your city. You can read more about this building and many others here.

When the march is launched, the distance between its destination and your city is calculated dynamically. That is, the march always starts from the closest point to the destination and returns to the closest point available. Since portals act like open gateways to your city, if a portal is closer to the destination than your city, then any march to that destination will start from that portal. It will also return to that portal given it's still open.

The player who opened a portal can close it at any time, even if allied armies are marching back to it. In this case, the marches will be redirected either to the next-closest portal available, or directly to players’ cities, depending on the distance between the marches’ current location and players’ cities.

Similarly, if you teleport your city closer to the march destination than the portal the march started from, your troops will return directly to your city.

Enemies can attack your city through your portal. Be careful: if an enemy army reaches your portal, it will ignore both your city walls and your shield of peace!