Livingmetal is part of the Harken Scythe mod and is created using an Altar of Souls to enhance iron bars. To do this, collect souls and deposit them in the Soul Crucible, which must be placed properly so that it functions correctly with the Altar. Livingmetal ingots can also be found very rarely in dungeon chests. Some rare/ultra mobs can also drop Livingmetal tools/weapons.
5 souls will imbue one Iron Ingot and convert it into a Livingmetal Ingot. The Ingots can then be used for a number of crafting recipes, and the Livingmetal itself has a unique property.
Livingmetal has a connection with the Asgard Shields mod meaning that you can also make giant swords, shields, and guilded shields.