Helmets are headwear that provide protection against damage from spikes, players, mobs and fires when equipped. However, they don't help reduce the cold, like the Chapkas - this means players have to sacrifice one advantage for another by wearing headwear.
Helmets are generally used for combat, especially since they seem to protect more against other players as opposed to mobs.To craft any type of helmet, players are required to use a workbench.
The Stone Helmet is the lowest tier of helmets, and provides the lowest protection. They are useful, however, at times, especially in the earlier stages.
The Golden Helmet is the middle tier of helmets, and provides considerable protection. They can be advantageous especially when fighting players without helmets.90 wood, 90 stone, 90 gold, and a stone helmet is required to craft the golden helmet.
The Diamond Helmet is currently the middle tier of helmets, and provides strong protection.100 stone, 100 gold, 100 diamonds, and a golden helmet is required to craft the diamond helmet. It takes 1 minute to craft the diamond helmet, therefore it is recommended to have an IKEA Manual or full health and cold bars before crafting the diamond helmet.
The Amethyst Helmet is the second highest tier of helmets, and provides a very strong protection.150 gold, 120 diamond, 80 amethyst, and a diamond helmet is required to craft the amethyst helmet. Since it takes 2 minutes and 20 seconds to craft the amethyst helmet, it is required to have an IKEA Manual in hand before crafting to survive.
The Dragon Helmet is currently the new highest tier of helmet, and thus provides maximum protection. It was added in the Chrono Quests update.