Arcane battery

An arcane battery is an artificially created energy source that draws from local leylines to power various magical effects. For this reason they are also sometimes called arcane accumulators. The spell engines of Avalir had twelve similarly named but much more powerful Eldritch Batteries. Many arcane batteries powered automata, like golems. In the Post-Divergence, arcane batteries are scavenged from ruins across Exandria.

Description
Arcane batteries are gem-like, polished spheres with cloudy centers. They are lighter than gems or similar materials, and they do not feel as a solid gem does. They vary in size, depending on their use and make.

They are of various colors and give off variously colored light when active and crackled, flickered, and hissed with energy. A battery found in a golem in Aeor was red, another found in an aeormaton was colorless, and batteries in Ira Wendagoth's and Imahara Joe's workshops gave off light that varied from bright blue to turquoise. The Eldritch Batteries of Avalir glowed various shades of green. Runes for enchantment in a device tend to glow the same color as the battery.

The batteries draw arcane energy from local leylines to power enchantment of various effects, ranging from animating automata to maintaining abjuration spells. They are primarily used in magical devices. Arcane batteries are capable of powering such devices for extended periods of time. For example, the Gear Warden created by Cleff Tinkertop is powered by a single arcane core and is designed to remain operational for two hundred years before the core needs to be replaced.

Age of Arcanum
Arcane batteries were used throughout the Age of Arcanum by skilled archmages. Caleb Widogast found that a Collar of Silence from the Folding Halls of Halas needed one to be recharged and believed that Halas Lutagran's golems were powered by them as well. Further batteries were found in the ruins of Aeor.

The Eldritch Batteries of Avalir, a flying city in the Age of Arcanum before the Calamity, powered the cities numerous spell engines and kept the city afloat while it traveling along the world's leylines. There were a total of twelve batteries spread throughout the city's neighborhoods. The batteries were attacked by k'nauthi cultists dedicated to Asmodeus who sought to release the two primordials under Mount Ygora so that they may fight alongside the Betrayer Gods against the Prime Deities. The majority of the attacks were successfully repelled by the city's defensive forces; one battery was taken offline and defaced in Primordial with the names of the two primoridials to attempt to wake them. Calum Staffwright reconnected the battery as he died, just as the Astral Leywright drew energy to banish the primordials from Exandria.

Post-Divergence
In the Post-Divergence, by 836 PD, arcane batteries were scavenged from the ruins of Age of Arcanum cities throughout Exandria and sold.

Vox Machina was contracted in 809 PD by Quall (via Drez Vina) to retrieve a power source, called an arcane cortex, from an iron golem in Shadebarrow.

The Mighty Nein salvaged a battery from a Centurion Automaton golem in the ruins of Aeor in 836 PD. This battery was located in the golem's head and was attached to the rest of its mechanics using a rubbery hose. It was used to repair the Collar of Silence. They similarly scavenged a battery from an aeormaton elsewhere in the ruins and used it to make initial repairs on the aeormaton Devexian. Devexian's previous battery, which was damaged, shattered upon removal from his body.

In Jrusar, Marquet in 843 PD, the fey Ira Wendagoth had an arcane battery in his secret lab to power an unspecified effect. Elsewhere in Marquet, Imahara Joe, an artificer in Bassuras, bought and traded for many arcane batteries to power his constructs, such as crawlers. Birdie and Oleander Calloway visited him every few months to purchase whatever batteries he could spare.