If you've spent time exploring the darkened burial chambers and slurpy swamps of Valheim, you've probably collected your fair share of surtling cores. The glowing, presumably evil cubes can be used to craft some of the most important items in the game like smelters, kilns, blast furnaces, and fast-travel portals. Early in the game, surtling cores are a pretty precious resource that takes a lot of dangerous work and exploration to find.
So you've no doubt been storing your surtling cores carefully in a chest, doling them out only when you need to build an important device or set up a new portal in a remote destination. Chucking a surtling core haphazardly into your campfire? It probably wouldn't be your first instinct.
But if you do it, you get a heck of a nice treat. Putting a surtling core into a campfire or bonfire turns it into a missile that launches straight up in the air and explodes. Valheim's got fireworks! I had no idea.
The only downside of throwing a surtling core into the fire (you can do this by putting a core in a numbered item slot and then pressing that number when you interact with the fire) is that the core is completely destroyed. But it's a pretty fantastic show, especially at night, bathing the surrounding area in a nice, warm glow. It could be a fun way to celebrate a victory over one of Valheim's bosses, or maybe to signal another player that your base is under attack, if they happen to be nearby and off mic.
Or maybe there's a larger purpose for fireworks we haven't discovered yet. In the meantime, they're pretty to look at, though don't get too used to putting on shows unless you've got a whole heck of a lot of spare surtling cores lying around.