Burial Chambers, Sunken Crypts, Frost Caves, Jotun Skulls, Infested Mines and of course Vegvisir locations are all subject to the laws of probability. Before starting a game I like to bring a seed up in the world generator[valheim-map.world] once with all locations highlighted just to show that when I actually start the game that my inability to find any of above is due to my poor or lazy exploration skills and not some imbalanced rng.