In Subnautica: Below Zero, every item has a purpose. In some cases, these purposes are somewhat limited, with items like Creepvine Samples being used solely to make Fiber Mesh. In other cases, though, an item can be used in a multitude of recipes. Crystalline Sulfur is one such recipe, as players will need it to make six different items at the Fabricator. These are all very useful items as well, making this resource something that players will want to hunt down from time to time. For this reason, it's important to know where Crystalline Sulfur spawns, as it is somewhat unique in this aspect compared to other items.
Many of the ores in Subnautica: Below Zero simply spawn either on the seabed floor or as part of Outcrops, but Crystalline Sulfur is different. There two main ways to acquire it, and both will have the player stepping outside of their comfort zone to a degree.
The first place players should look when searching for Crystalline Sulfur is on Delta Island. Throughout this area there are concentrations of a yellowish liquid known as thermal pools. Standing in these will warm the player up, helping them get further into the island without freezing to death, but Crystalline Sulfur can also spawn around these pools as well. Beyond that, it can also spawn on the walls of the caves on Delta Island, so players should search those too. Be sure to use the Thermal Lilies to maintain warmth while exploring or use Subnautica: Below Zero's Cold Suit to stave off the freezing temperatures.
Outside of this, Crystalline Sulfur can also be harvested from Sulfur Plants. This strange flora can be found in the Arctic Kelp Caves, Crystal Caves, Crystal Castle, Purple Vents, Twisty Bridges, and Twisty Bridges Caves biomes, but harvesting the Crystalline Sulfur from within won't be easy. When the player gets too close, the flower sprouts open and a Crashfish will swim out to charge the player and explode. The bounty inside can only be harvested once the accompanying Crashfish is dead.
Players can use the Crystalline Sulfur they've collected at the Fabricator to craft Flares, a Repair Tool, a Laser Cutter, Gas Torpedoes, the Prawn Suit Jump Jet Upgrade, and the Seatruck Afterburner Upgrade. That Seatruck upgrade is particularly useful, as it allows the player to use a short boost at the cost of energy when piloting their Seatruck through Subnautica: Below Zero's expansive ocean.
Subnautica: Below Zero is available now on PC, PS4, PS5, Switch, Xbox One, and Xbox Series X.