In Dawn of Titans you are trying to become the most powerful Kingdom by battling other players and increasing the reach of your empire to earn Victory Points or VP. Muhahahaaa! Yes, we will allow you to 'evil laugh' after your victories.
Battling other players will cost Portal Stones, a resource which slowly regenerates over time. You can attack other players' Lands by either Raiding them to steal resources, or Capturing them, which will put the Land under your control and generate resources for you over time. And generally to make your kingdom look more epic and imposing to others, (evil laugh again?).
But beware - if another player captures one of your Lands they'll take control of it, so make sure you keep your Kingdom well defended. No one likes a naked kingdom now, do they...
For more information please visit our official Dawn of Titans Wiki page!