Overview
Crypt4 is a Valheim world location that spawns in the black forest biome, identified internally as Crypt4. World generation places up to 200 per world, with terrain constraints (max delta 2), and an exclusion radius of 18 (21)m, which is why some seeds have far more of them than others. The data tags it as interior randomly generated and vegetation allowed.
About
Crypt4 is a Burial Chamber dungeon variant in the Black Forest with a randomly generated interior. The dungeon's chests reliably yield Surtling cores for Smelters and Charcoal kilns.