In Viking Gods, your rooms will earn Iron every second of the game.
By upgrading your rooms, you'll increase the amount of Iron you're earning. Each room displays the current amount of Iron it's earning per second.
At certain points, upgrading a room will level it up, making the speed of earning increase, and giving the realm more tap damage.
After time, the realm will begin to be raided by skeletons and ice giants. You'll need some help defending your rooms.
You'll earn Champions, like Big Erik, Thor, and Slepnir, by defending the realm against raids. By completing each raid, you'll earn a chest, which will contain new Champions or duplicates of them that will help you level them up.
By completing raids you'll also earn Glory. By causing Ragnarok, you'll be able to use that glory to upgrade your relics, powerful items which will make your rebuilding of the realms much faster, and make raids easier to battle, allowing you to get further in the realm and the story.
Continue playing the game, fighting against raids, upgrading rooms, and levelling up your Champions to progress through the story and get to the end of the game!