This is a port to 1.16.5 and later, of the Arsenic and Lace module of akkamaddi's Additions from 1.7.10. See that article for original permissions and Minecraft Forum thread links. The mod (an add-on for Simple Ores) was originally written by akkamaddi, and then abandoned; I took up maintenance of the mod after that.
Adds the materials arsenic, arsenide bronze, and arsenide gold, as well as old lace burial shrouds. Arsenic has no ore, and is derived entirely from the Fusion Furnace. Now with Tenebrium!
Long ago, people would preserve taxidermy with arsenic salts. Recently we have learned that the dark forces that create the zombies of Minecraftia use these same materials to preserve the spawned zombies! By using the magic of the Fusion Furnace, one can fuse rotten zombie flesh with either skeleton bones, or slime balls, to distill the minerals orpiment and realgar. This starts a chain of events to create ingots of refined arsenic. This can be used to make tools, but arsenic is a brittle metal, so it cannot make armor. Arsenic can be alloyed with copper to make arsenide bronze, and gold to make arsenide gold. These two alloys are strong enough to make armor as well as tools. Additionally, arsenide gold can be alloyed with obsidian blocks to make the glassy material Tenebrium, which makes very durable tools and armor.
Further, we have found that the arsenic sometimes preserves the Old Lace Shroud in which the dead were originally interred.
Arsenic tools are comparable to wood, though with a slightly higher durability, and a higher enchantability. They are repaired with arsenic ingots.
Arsenide Bronze tools are comparable with Bronze tools, but with a slightly higher durability, and higher enchantability. However, the are not as sharp, and standard Bronze tools work a little faster. These items are repaired with arsenide bronze ingots.
Arsenide Gold tools are comparable to Gold, with a slightly lower enchantability, but a higher durability. These items are repaired with arsenide gold ingots.
Tenebrium is between diamond and onyx in most aspects except durability. The durability of tenebrium is exceptionally high.
As of Minecraft 1.18.1, a rare arsenic ore has been added to the world, as well as the darkly poisonous Necrotic Furnace. As designed by akkamaddi:
"The Necrotic Furnace is a basic furnace with a second output in the lower corner. It runs on necromantic energy. Rotten Flesh and Bones smelt eight items, and bone meal smelts one item. (A Shroud could fuel 64 item smeltings, and bone blocks smelt 80 items. The heads of undead monsters may fuel the furnace as well.) Each smelted item has a 25% chance (configurable) of generating one Toxic Soot in the lower output. Toxic Soot items can be combined to a Toxic Lump, which can then be smelted into an Arsenic Nugget. This lets people with massive stores of zombie flesh use it as a useful fuel, while providing a slow trickle of arsenic for alloys. Also, cooking food in an arsenic furnace over zombie flesh releasing its necromantic energy gives it a lovely roasted almond flavor, and is great for weight loss diets as your fingers and toes fall off."
Cooking meat in the Necrotic Furnace turns it into rotten meat, and cooking potatoes (or other configurable vegetables) turns them into poisonous potatoes. If you or your modpack maker decides that being able to farm fuel by cooking meat in the Necrotic Furnace is too much of a good thing, this feature can be turned off in the config file.
Further documentation, including recipes, can be found on the wiki.
