The cause of their orcs invasion was a severe famine. The Magic Continent is a land with fertile soil under the protection of the demon lords. Many powerful demonic beasts and demons inhabit it, but thanks to the demon lords, it is safe. However, there was a price for safety, a steep tax. Those who wanted to live on fertile lands had to provide a large amount of crop. Orc, who reproduced quickly, worked in the mines and toiled the fields, were necessary to the demon lords. However. Those who could not pay taxes were immediately killed. The demon lord never lended a helping hand. Aiming for the abundant resources, many monsters attack. Those who had not paid the protection tax were not protected. Thus that land inevitably became dangerous.
The fertile orcs, even if the majority of them were killed, would soon enough restore their population to needed levels. Though there was a need to control their number, the demon lords decided that the extras would die anyways. Now, thanks to a great famine, they could not pay their tax. Thus, losing the protection of the demon lords, they decided to flee those lands in search of a safe haven. While beset by hunger, the Orc Lord was born, but until then they would never fought anyone stronger than themselves.
And thus wandering, they have made their way to Jura Forest’s outskirts. Around that time, Gelmudo offered them a hand. Oblivious to his machinations, they decided to accept his offer. Thus, following his directions, they plunged Jura Forest into chaos. This led to the extinction of the ogres and their numbers decreasing from 200,000 to 150,000. And the orcs excel at manual labor.
Due to Rimuru’s involvement, they were given the lands away from the marshes. Those originally owned by the ogres. That place is also by a foot of a mountain with abundant resources. All 150 thousand couldn’t possibly all live on the same land, so the particularly large clans split into individual districts.
The great clans were separated by their names: Yama (mountain) , Oka (hill), Hora (cave), Umi (sea), Kawa (river), Ko (lake), Mori (forest), Kusa (grass), and Suna (sand). For example, a man from the mountains would be “Yama-1M.” A woman would be “Yama-1F.” For kids “Yama-1-1M,” for example.
After being named, the orcs evolved into high orcs. But since they weren’t named using Rimuru’s magical energy, there was no master-servant relationship between them. Their strength did reach up to C+ immediately after evolving, but they settled comfortably in the C rank zone. More importantly, they got smarter while preserving their special characteristics. They evolved into a race that could adapt to and make use of any situation.
There is very little variety at first; basically limited to a growing a potato-like crop, that grow even in harsh environments. It also has high nutritional value, and though one can’t exactly call it luxury food one can certainly live off of it. Thus, Tempest spread the seeds among them and taught them how to grow it.
Tempest established a communication network between all the villages, basically, a postal service.