Background
Fans of power metal band "Gloryhammer" might have already recognized from the title of this question that I'm talking about Knights of Crail as described in a song "Hail to Crail". For a short story I have in mind I want to imitate the pathos and awe of that song and create basically a carbon copy of Knights of Crail, a tribute to the band I love and song that inspired me to write this story. In my story, the undefeated warriors loose a fight against advancing "great, bad empire" which creates the motivation for the main character to seek vengeance and kick-starts the story. The only difference between my warriors and warriors from the song other than name is that they are real life warriors from late iron age, since eagle warfare doesn't fit the "alternative history" setting I'm going for.
Problem
The part I'm struggling with is that, according to the song, Knights of Crail are "fighting battles every day". I don't know of any non-nomadic cultures, where that would be sustainable for an extended amount of time. Even if my warriors were so good that they never loose anyone in battle, eventually there would be nothing to raid and nobody to fight. If possible, I would prefer that those warriors don't travel a lot (no further than a horse could reach) and stay in the village most of the time, so viking-style raiding is not an answer I'm looking for.
Celts where ferocious warriors and my first choice for inspiration, but for most of the time they maintained peace with surrounding tribes and enjoyed their social position at the top of society. Aztecs are an interesting choice, history of Mexica people is absolutely bonkers and full of senseless bloodshed for the god of war they worshiped but the only reason why Aztecs where not annihilated is because they knew when to lay low and when to strike. If people in my story where anything like those from Valley of Mexico, in response to constant harassment my tribe would swiftly be destroyed by an alliance created to oppose it.
Additional info
Although not directly related to the question "how can iron-age sedentary warriors fight every day and not run out of people to fight", below information might be helpful to answer the question.
- I need to make sure that the reader feels the same veneration towards those warriors as the main character, so I'm overplaying their role in keeping the village safe and downplaying any horrors of war. Any glorification of killing needs to be omitted. The fighting needs to be justified in the eyes of contemporary readers. No killing of the weak and defenseless.
- My village needs to be unique in its strength among other villages. It would be nice if those warriors where also venerated in neighboring villages, their fights benefiting the community at large. It's okay if their superiority came from their training alone and plot armor, it must be clear that even if all friendly relations were severed they would still prevail without any danger.
- The superior strength of warriors from my village has been maintained over generations so whatever the explanation is for never-ending stream of people to fight, it must hold for at least few centuries.
- Warriors of this village are a significant cultural element of living there. Although I could work around the warriors not returning home every night, I imagine them returning to the village after battles every evening and telling their stories with a beer in hand while enamored youth listens in awe and admiration.
- Despite possessing military might over generations, nothing reminiscent of an empire should form. This is important for the narrative reason because it plays into a theme of inevitable social progress and "new" defeating the "old" ("age of warring tribes" defeated by the more advanced "age of empires") and a theme of success turning into a weakness (undefeated warriors never had a reason to adapt to modern times and imperial social structures seen as inferior, never had a reason to join forces with other tribes and form alliances).
Possible solutions
At the moment I have two ideas that could work but what I'm really not sure about is the number side of things. Even if just two opponents die in a battle every day, that makes over 700 deaths every year on the opponent side. If we consider that most of the opponents are captured and not killed this gives a gigantic, very minimal figure of 1400 slaves a year, totaling a 2300 population drain every year. That's without counting all the "epic fights" they are trained for.
First idea is that the geographic area where my village is located is modeled on Mycenaean Greece. People slowly concentrate in urban centers, devoting themselves to life of agriculture and trade and roaming bands of bandits still outnumber the settled population. My warriors leave their fortified village everyday to search for and capture or scare away those bandits, keeping the tracts safe and trade prospering. The bandits present a danger to traveling merchants and field workers but not to the fortified village. Similar but slightly different idea is that my village is located at the choke point between mountains and the sea and nomadic tribes constantly try to cross that choke point to reach worse defended areas to raid. Those ideas are not mutually exclusive and will together provide a sizable amount of foes to fight for my warriors. But I'm not sure if "every day" is guaranteed here, especially if they fail to track any enemies.
Another idea is that "great, bad empire" is close enough to the village to raid and is not very well defended for some political reason. "Real life" example of this would be a hypothetical Celtic tribe that refused to sign a pact of non-aggression with Roman Republic. My village would keep harassing them but for some political reason or because of previous defeats the Republic never did anything about it. Maybe warriors were not bordering the Republic but were secretly provided safe pass by a tribe friendly to the Republic and Romans couldn't counter-strike without invading their allies, which would result in all surrounding Celtic tribes collapsing on them in a war Rome knew they would loose. If my tribe was located close to an equivalent of Germanic tribes they could go riding either way, splitting the damage between those two regions and making it less impactful. Again, the numbers of casualties from everyday fighting seem way too big to be realistic but by spreading them over maximum territory perhaps it would allow time for those regions to be repopulated and ready to be invaded again. Going this route it would be a bit harder to paint the warriors as knights of justice but a subtle spin of "they started it" and "everyone does it anyway" should be enough.
Originally I wanted the empire to be completely foreign and appear suddenly and this idea contradicts that. However what I love about it is that sudden shift in balance of power between the tribes and the empire can be caused by the end of war in a far, far away land and ambitions of some imperial politician, making the grand, larger-than life warriors and their village from the first chapter feel even more like a small and insignificant part of the larger and indifferent world, where barely no one can make a significant impact.
Question
Although already stated multiple times, I'll reiterate the question in full, since this post turned out really long and full of details.
In a realistic setting, mirroring late Iron Age in our history, how could it be possible for a party of non-nomadic, possibly horse-riding, undefeated warriors (meaning that casualties are incredibly rare) to fight battles every day and return back home at least every few days over the span of generations and never run out of enemies to fight. At the same time, those warriors cannot engage in behavior that would paint them as obvious villains to contemporary readers, like killing and kidnapping defenseless farmers. Killing and kidnapping other warriors is permitted, as long as this is a norm in both cultures. The impossible superiority of warriors doesn't need an explanation, they just are undefeated by the power of hand-waveium and eventually defeted due to being outnumbered, outmaneuvered and outequipped by a larger-than-life power.
I'm especially interested in numbers of casualties and ways to lower the impact of those casualties over the area, since even lowest estimates give numbers that scale to huge proportions over a year of every day fighting.