COAL

Winter Wonderland event currency — the 'naughty' half, and the one fewer recipes ask for.

• A second event currency, not a fuelDespite the name, Coal burns in nothing. It exists to be spent on the Winter Wonderland recipes listed under Used To Craft, alongside Mistletoe. If you want something to burn, that is Wood, Sparkpowder or Gasoline.
• Comes from the same two sourcesRaptor Claus's drops and Gacha Claus. It is the half you get more of than you need, which is why stacks of it survive the event.
• It only exists during the eventWinter Wonderland runs for a few weeks around Christmas and the recipes it unlocks are only craftable while it is live. Outside the event the items stay in your inventory but nothing new drops.
• It spoils — so hoarding between events does not workThe spoil timer on the Facts panel runs down in any normal inventory. Keeping a stack for next year means a Preserving Bin or a fridge, and even then the plan is usually to spend it before the event closes.