As the game stands right now, there is no real need to explore much aside from finding the bosses and finding decent sizes of each biome. And once you have beaten the bosses there is really no need to continue exploring.
Valheim could implement a perks or magic system. There are already weapons that have some magical properties so I am not asking for anything that is not already a part of the game.
My idea would be to turn the valuable items into socketable items. Like the ruby adds fire. The amber adds lightning, etc. But you can make it in such a way that these items only spawn in certain dungeons spread out across each biomes. You could add a jewerly station where you have to combine these jewels, like say 10 rubies for one enchantment. Another idea would be to make it so that a specific item is need to even add sockets to a weapon/armor piece.
You could even make these very difficult to obtain by placing a locked chest next to an alter of sorts and each alter spawns a number of 2 star enemies depending on the biome. Such as dark forest, spawn five, 2 star Trolls. Defeating all the enemies opens the chest containing the enchantment items.