When the mirror woman of hell created machines of glass for war, she found it easier to discard the maimed survivors of war rather than repair them, since she could create new ones easier than repairing ones that had already been damaged. The damaged machines left her service and bounced from town to town, rejected because they were weapons of war and because they had fought against many of those residing in the various cities of hell. They founded the city of Scrapyard, where discarded machines go to live out the rest of their days, or where sentient machines go to escape servitude. The machines did not have emotions, but a very talented artist and roboticist in the underworld was able to create something for them.
An automaton heart is an energetic construct that attaches to the soul of a person and floods them with emotions that are appropriate for the situation they are in. Most can be set to be purely positive but many automatons choose to get hearts that accurately reflect what the average person would experience in a situation even if it is negative.
Automaton hearts have two variants. The first is the radiation based model which appears like a lantern, but has a strong energy inside metal and paper which gives its user emotions by radiating energies from inside of their chest. These are the most common types of automaton hearts and are the easiest to mass produce due to their simplistic design and method of function. The second kind are the more complex mechanical ones for those who need access to more complex emotions and sentimentality. These appear as metal or gemstone hearts with valves, pistons, gears, or outlets, circuitry, or wires. Users of complex hearts typically tend to have lots of conflicting emotions but are also better at reading social situations and responding appropriately to complex topics. These are primarily used for therapists drones or those caring with people for PTSD or other conditions that require them.
To cast a spell of automaton heart on yourself, go ahead and invite it into your heart center. You may not need one if your heart chakra is functioning but otherwise it will simply boost it. While meditating, call upon the exiled robots or the engineers of the spirit world to grant you an automaton heart.