Eternal by Roman Zlotnikov

Humanity, having reached the Space more than a hundred years ago, fights against an aggressive civilization which contains a huge number of races and species and tries to take people over, too. There’s a more peculiar point, as the leading race representatives look like devils. They are extremely strong and viable and, moreover, have ability of hypnotizing sentient beings and controlling them. They are rumored to be almost immortal. Also, among the creatures they control there are legendary ones such as tolls, orcs and demons.
Due to the specific of ultrahigh space physics, which allows to exceed much the speed of light, the warfare turned back to the age of pirates of the Caribbean. It turns out that offensive aid in ultrahigh space lost its efficiency, but when the ships approach each other, no matter at which angle even head-on, they can not help moving in course line. As a result, close and boarding fight came back into use. Thus, technical excellence dives way to personal courage and dare to meet the enemy in hand-to-hand battle.
Owing a lot to this fact a new brotherhood (if not a class) of professional warriors has emerged, and they receive the name of ‘Dons’. This multinational and multicultural society is highly religious due to the specifics of the clash. A lot of customs and traditions popped out, such as obligatory moustache for men or personal nickname, some of them quite curious as Balky Bull, Fungus Face or Beer Cask, often pointing out the most important feature or trait. Futhermore, nicknames such as Ironhand or Blackdeath would immediately inform any Don that its owner is a dude never been in a combat. Unlike nicknames, surnames are not as frequent, neither are other means of identification. It is widely believed that a man cuts himself off his previous life by joining the Dons.
Yet, the war with ‘Devils’, much better known as ‘Red Princes’, has raised the religious spirits of the society. It happened more or less in this or that country, however, soon after the war broke out, the Pope declares the restoration of religious orders. Also men spread all over the galaxy have created quite a few new social institutions. For instance, there is a kingdom where men and women exchanged roles completely. Women used to be warriors there while the men were mostly househusbands.