Thulecite is a craftable Item found in the Ancient Tab. It requires 6 Thulecite Fragments and a Broken Ancient Pseudoscience Station to be crafted. Thulecite is generally acquired by destroying Ancient Statues and Ruins Sinkholes with a Pickaxe, Gunpowder etc., but they also have a 10% chance to be found in Ornate Chests and a 75% chance in Large Ornate Chests. Thulecite also can randomly drop when destroying Relics or damaging Ancient Pseudoscience Stations with a Hammer, Gunpowder etc. Like all items from the Ancient Tab, Thulecite cannot be prototyped and Characters must stand near an Ancient Pseudoscience Station to craft them.
Its main use is as a crafting material for items in the Ancient Tab. It can also be used to repair a Broken Ancient Pseudoscience Station, opening up more crafting options.
In the Reign of Giants DLC, players have a small chance of finding Green Gems inside Tumbleweeds, thus making Thulecite renewable, since more Thulecite can be gained with the use of Construction Amulets and Deconstruction Staves as explained below.
In Don't Starve Together, Thulecite can be gathered in the Caves from Cave Holes with the The Lazy Forager. After killing the Ancient Fuelweaver, an event triggers that respawns the Ancient Statues in the Ruins, providing a renewable source of Thulecite and Gems. Players must wait 20 days until the Fuelweaver can be fought again.
With the Forgotten Knowledge update, Thulecite can also be gathered by utilizing the Dust Moths found in the Ancient Archive. After feeding one an Amberosia, it will begin to ornate a nearby Tidy Hidey-Hole with mineable Thulecite Fragments. Because Amberosia is renewable, this provides a reliable (albeit slow) source of Thulecite alternative to killing the Ancient Fuelweaver.
- Although Green Gems are somewhat rare, it is possible to use a Construction Amulet to craft 5 Thulecite Suits for 15 Thulecite, then use a Deconstruction Staff on those 5 Thulecite Suits to get 30 Thulecite back for a profit of 13 Thulecite (the Amulet costs 2 Thulecite). This practice makes it possible to collect big amounts of Thulecite from a few Green Gems.
- Slurtles, Snurtles and Rock Lobsters will attempt to eat dropped Thulecite, so players should be careful and collect all Thulecite before they successfully eat it. Slurtles will also attack a player holding Thulecite if there aren't any other minerals around for them to eat.
- Thulecite may have been based off of real-life mineral thulite, which is also a variety of zoisite.
- Like much of the Ruins, Thulecite was inspired by the Cthulhu Mythos, and may have derived its name from the name of Cthulhu, an ancient god-like being associated with insanity, magic, abnormal geometry, and tentacles.
- A secondary inspiration for the name may have come from Thule, a northern region in ancient geography that is usually described as being the farthest north one can travel. Later, writers would use the term Ultima Thule to describe something far off and unattainable. This is more than likely inspiration for Thulecite's status as an endgame material.
- The material itself is quite similar in color and use to the Dwarven Metal that is found in the The Elder Scrolls series, as both the Dwemer and the Ancient Civilization used their own material (Dwarven metal for the Dwemer, and Thulecite for the Ancients), and when they became extinct, their respective material were left behind and could be used by those who found their ruins. This is perhaps unsurprising, as it's a believable explanation for the rarity of the resources required for rare elite items.