Calefaction levels could be gained by smelting items in a furnace. While standard smelting would still yield experience, smelting ores yielded a considerably larger amount of experience. When your Vitality resource bar was high enough, it gave the player a crit chance depending on the level. The critical damage stacked with vanilla Minecraft critical hits, and while it normally only affected melee weapons, ranged weapons could be given the critical chance if the player wore the Calefaction Armor. The critical chance and damage for levels were:
