Demons are a complicated set of creatures, and while their very nature leaves them near-endless in the forms and lifestyles they take and adapt to, there are seven key states they tend to have in their life cycle.
Stage 1: Existence
A demon is formed when a living being has their first negative experience, typically through either anger, fear, sadness, or disgust. Due to how infants typically work, this happens not long after their birth. Beginning as what appears to be a miniature nebula of spiritual energy orbiting its core, they are a literal maelstrom of negativity that is slowly pulling itself together. If a mortal being were to interact with it, the most that usually happens is a heightened sensation relating to the reason they were formed.
This one, observed as our example specimen, was formed from sadness of some kind.
Stage 2: Coalescence
The demon has managed to take a physical shape, but is only just learning how to utilize its body. Though there are exceptions, these stages tend to resemble single-celled organisms. The unique difference between mortals and demons is that demons are made entirely of this energy no matter what shape they're in, sculptung themselves on a molecular level with the ease of flexing a muscle. Lacking any form of nervous system, they begin to develop into what they are truly intended for; Consumption of matter, and most especially the life force of other beings. Lacking brains, they will typically try to eat anything that they make contact with, but will only gain true sustenance from the residual emotional energy of other nearby beings or that lifeforce itself.
In this case, our star seems to respond the best to feelings of joy. Its a rare preference for demons, but one that typically pushes them towards being social and making connections.
Stage 3: Formation
Demons still maintain an intrinsic connection to the person they were formed from on an emotional level. Though this connection weakens as both develop, the final major surge of influence that this connection has is the third stage in the demon's life. The demon will reflexively take on a form evocative of the first thing to terrify the mortal they were spawned from, gaining the proper context for their own thoughts a full body allows. While they will develop further later, elements of this shape will typically be subconsciously added to any form they take going forward.
Looks like this one's originator was scared by a beetle of some kind. Flight and a tough shell are a lucky combination to have in environments as hazardous as the demonic realm, as is the inclination to scavenge it provides. Feeding will be a slow process, but there is no shortage of carrion where it lives.
Stage 4: Contemplation
This tends to be a make-or-break situation for the creature. Based on their environment and the lingering influence of "their" mortal, they will grow to learn and truly fend for themselves. If things remain simple, then the demon will typically remain in a state of mostly-feral apathy towards anything near it, provided it can still get what it wants.
On the other end of the spectrum, the demon is likely to begin making note of the world around it, listening to what stronger creatures say and internalizing it. Our subject happens to have the benefit of looking unassuming and generally beneath notice, so they're free to stop and think all they like.
Step 5: Self-awareness
At the end of this contemplation of the world around it, the demon will at last turn its thoughts inward. It heals from any harm, but why? It needs to eat, but plain old meat and plants don't cut it anymore at this size and complexity. What is it actually eating? And how does it get more?
The lynchpin question that pushes their biggest evolution however, is "If I changed shape already, can I do it again?"
Its at this point that demons begin to undergo enormous shifts in behavior as they test their limits. They gain ambitions, make goals, and eventually, sneak into the mortal realm sensing a higher abundance of the energy they need. It is there that they either find their niche on their own, or throw their lot in with a stronger entity, demonic or otherwise, in an effort to survive. Not many advance past this stage of their life, mired in the complacency and fear that comes with the environment they were thrust into. Others, however, go even further, taking on forms that resemble weaponry, shadows, or even splitting their body amongst many smaller vessels.
Our beetle friend has a lot of thinking to do, but at the end of it all he'll become the best version of himself.
Step 6: Resolution
The demon begins to finally understand itself. It takes on everything that it's experienced and begins to put it to use. Pushes the limits of their body, mind and soul to do more bold and intensive things to survive, and thrive. In the end, it does something beyond mimicking what it's seen before, and crafts a body for itself that represents everything it wants to be.
Our subject isn't having the best time, but he's determined to see himself through to the end.
Step 7: Apogee
At the end of it all, the demon has finally reached the apex of its evolution as an individual. No longer simply the dark side of another, it has become an entity that encapsulates everything they've known and everything they want out of life. Some want to be something so horrific that none will dare attack them. Some want to be something so unnoticeable that they will never know they're there until it's too late. But some, very rarely, seek to become someone. Someone who is able to interact with the world around them, take in the sights, and live a life of peace they were denied. For many, it's a torturous experience, but ultimately one worth the blood, sweat and tears.
Our star started as an object of fear, and born of sadness. But in his pursuit of self, he finds everything all the sweeter when he defied that origin, and chose a form suited to making people smile. Bits of a jester, bits of a dancer, and a reminder of what he started out as to remind himself of how far he's come. He'd decided on a name before, but now he has the satisfaction in his heart to share it proudly. He is Burzen.