The bruma torch is a possible reward from the Reward Cart after subduing the Wintertodt. When worn during the Wintertodt boss fight, it acts as a warm clothing item, and it can also be used as a replacement for a tinderbox for the purpose of lighting braziers, regardless of whether the torch is equipped or in the player's inventory.
Around the game world, the torch acts as a light source that can be equipped, but does not function as a tinderbox. It has no possibility of triggering the explosions in the Lumbridge Swamp Caves. It can also be used in place of a lit torch when smoking traps.
Players can trade in bruma torches for an extra supply crate or 50 burnt pages via Ignisia. If a player has three bruma torches in their bank and/or inventory and/or Magic wardrobe in a POH, searching the reward cart will give 2-3 torstol seeds when it would have given another torch.[1] Currently the Grand Exchange price of 50 burnt pages is 290,600 and the price of a torstol seed is 15,463.
It is generally more beneficial to exchange spare torches for 50 burnt pages, unless you are an ironman who wishes to receive torstol seeds. Note Wintertodt's unique rewards cannot be received from the extra supply crate.
The torch can be swapped via the "Swap" option, converting it to its off-hand variant so that it can be equipped in the shield slot. Both versions are storable in the magic wardrobe.
The Bruma torch can now be used to light braziers and smoke hunter traps.
Trivia
Bruma is a Latin word meaning "winter solstice" or "winter".
References
^Jagex. Mod Ash's Twitter account. 14 May 2018. Archived from the original on 29 July 2019. Mod Ash: "The dev who made that table does indeed appear to have written it so that if the game's thinking of giving you gloves, and you already have 3+ pairs, it'll give you a magic seed instead. Same for torches and the torstol seed. It's an unusual bit of code, but looks intentional."