There are several items you can craft to use as a fire in Valheim. You need a fire to cook your food, increase your comfort, and make sure your bed is warm so you can sleep at night. During the first portion of the game, you’re going to use campfires, and it’s a cheap enough crafting piece that you can make several of them. Eventually, when you learn how to create a stonecutter, you can replace your firepit with a hearth.
The heart doesn’t require advanced resources. You won’t need to use bronze, iron, or even copper. Instead, the only ingredient you need to make a hearth is 15 stone. The real caveat is learning to build a stone cutter. How you learn to make a stone cutter is by finding iron and smelting it as your smelter. You can gather iron by investigating the crypts in the Swamp. You won’t access them until you receive a Swamp Key, which you earn by taking down the second Forsaken boss, the Elder. It’s a guaranteed drop, and the item does not go away after you use it.
Once you have a stonecutter, you can then place it down in range of where you want to set your hearth down. Much like the campfire, a hearth has smoke rising from it. However, you can place it on wood, so you do not have to carve out the bottom of your house to make sure it’s touching the ground. Plus, you can place it on the second or third floor of your home, allowing you to create massive buildings and keep them warm.
The hearth is long enough to support four cooking stands, or cauldrons. You can cook and keep multiple floors warm, so you can place beds higher up in buildings you create if you have a solid foundation to support them.