Basics
Nardeae Owls are a type of undead, birds brought back to life through a combination of Nature Magic and Necromancy.
They do not need anything but sunlight, cannot die of old age, can drain energy from other living beings, and all plants grown on them are infused with magic. All of this makes them good long term guardians and familiars for many magic users.
Most of these Owls can fly, though if an Owl only has one wing, or was created almost entirely from a flightless bird, the Owl will not be able to fly.
History
The array used to create a Nardeae Owl was originally invented by a witch, some 400 years ago. She was obsessed with owls, and loved plants. She made several dozen Nardeae Owls in her lifetime, but only two still exist. Nardus, the very first, and Dante, the very last.
Her journal, which detailed the process to create one, was discovered by a passing Necromancer a few years after she died. Nardeae Owls have since become widespread, but the journal lost.
The Array originally could only be used on owl skeletons, but a few dedicated people have been able to change it so they could use it on other bird species. Even then, they still have to use an owl skull for it to actually work. Nobody has managed to make the array work on any other type of animal.
Creation
To create a Nardeae Owl, a Necromancer must draw the correct array. Then they must put a pile of dirt, a complete bird skeleton, and some sprouted plants in the array. The Necromancer may also put other things that can be functional or aesthetic.
The skeleton can be mismatched, but all bones must be from a bird of some kind, and the skull must be from an owl of any kind.
The plants should mostly be grass.
Then, the array must be powered for five days and five nights.
If done correctly, the dirt will attach to the bones, and begin to resemble the flesh of a living bird. The plants will attach themselves to the surface of the dirt, and take root. Any additional things placed in the array will attach themselves to the forming owl. Usually these will take the form of eyes, a beak and legs, but can also become many other things.
If there isn't enough dirt to cover all the bones, the owl may have visible bones. If there aren't enough plants, the owl will have patches of visible dirt. If there is less than about 25% surface area covered in plants, the owl will simply die again, because it cannot get enough energy.
Once the five days and five nights have been finished, and the Owl successfully created, the Owl will simply be a puppet. The Owl will slowly gain sentience over the next decade or so, until it reaches about the equivalent of a human. Sentience can be prevented by a major alteration to the standard array.
PERSONALITY
Nardeae Owls have two core temperaments, Aggressive and Peaceful. These are not completely inherent to each owl, but it is difficult to change. Not every owl will have one of these temperaments, but many do.
Personality beyond the core temperaments can be pretty much anything.
The core temperaments are decided based on how their original Necromancer got their bones in the first place.
Aggressive Owls were made from birds killed directly or indirectly by their original Necromancer. The owl will have an inherent grudge against them, and will take any chance it can to get revenge, even if they have no mind of their own. After the Necromancer dies, they usually wander. They can mellow out or begin killing everything they come across or anything in between.
Peaceful Owls were made from birds killed by anything but their original Necromancer. The owl is usually very loyal, and it takes a lot for this to change. These owls are the ones that willingly continue to obey their Necromancer's orders long after they've achieved full sentience and the Necromancer is dead. These owls can stay in one place or with one family line, and guard it for centuries. They can be violent or do terrible things to protect what they want to protect, but they usually won't seek out violence.
Other
Nardeae Owls do have gender, but they do not have biological sex. They cannot reproduce. This is because no flesh from the original bird remains.
Owls do not have to be companions to other beings, but they can benefit from it. They can easily turn parasitic if they want or need to.
If they don't have access to sunlight, they can take life energy from living beings or magical energy sources.
Nardeae Owls can die again if: they don't have access to the sun or an alternative energy source; their body is destroyed; or another Nardeae Owl drains them of their life energy.
Necromancers can be any fully sentient species with access to magic. You don't have to have a Necromancer or anything, but you can if you want.