The Reidite Protection is the highest tier of protection. It can be used to AFK in the Lava Biome. Please note that everything in the lava biome deals damage to walls so you will have to have a lot of walls to protect you from dragons and lava monsters (three amethyst walls are recommended). While wearing this, you need no Ice Cubes, except for crafting water bottles. In addition, you will gain no heat when near a heat source such as a firecamp. Unlike Diamond Protection, which only stops the red heat bar from increasing near a fire, this protection stops the blue cold bar from increasing.
To craft this item, you need 1 Amethyst Protection, 25 Flame, 100 Amethyst, and 100 Reidite. It is required to have a book equipped, as the crafting time without it is enough to fully drain the food and water bars.