A Lord From Planet Earth

A Lord from Planet Earth (Лорд с планеты Земля, Lord s planety Zemlya) is a Space Opera trilogy written by the popular Russian science fiction author Sergey Lukyanenko. It is Lukyanenko's first major work in this genre. Interestingly, the original draft was a Fantasy, but he realized early on the story would work much better as science fiction. However, many elements of the original fantasy version still remain throughout the novels. Unfortunately, the original draft has since been lost, so we only have the Word of God of its existence.

The trilogy tells of a former Russian Army sergeant who ends up on another planet and asked to save a princess. Despite the unfamiliar environment and technology, he manages to do it and falls in love with her. In the second book, he is trying to find and stop a group of religious fanatics from destroying a planet they consider to be the bastion of evil. That planet is Earth. In the third and final book, the hero and the whole galaxy are fighting a powerful enemy with Blue and Orange Morality.

Despite being a space opera, the trilogy owes much to its fantasy roots by focusing less on grand battles between armies and fleets and more on personal combat. The author even forces the hero to often engage enemies with his sword by utilizing Applied Phlebotinum that renders all other forms of weaponry useless.

The trilogy consists of the following novels:
 * The Princess Is Worth Dying for (Принцесса стоит смерти)
 * The Planet That Doesn't Exist (Планета, которой нет)
 * Sea of Glass (Стеклянное море)

The trilogy contains examples of the following tropes:

 * Antimatter - the protagonist uses two forms of anti-matter in a space battle in the second book. However, the enemy finds ways of neutralizing the threat. First, they activate the neutralizing field to prevent any destructive reactions. Then they detach the armor section with the antisodium on it. Next, the protagonist uses antihelium, which flows around the enemy ship, completely covering it. The enemy then starts heating up a single section of the hull, evaporating the antihelium, using the same flowing property to get rid of it all.
 * A bit of Fridge Brilliance here, as liquids have a lower boiling point in vacuum, so it wouldn't take much heat.
 * Blue and Orange Morality - the Fangs are a race of Human Aliens from another galaxy. While their appearance is similar to humans, their motives and thought processes are completely alien. They start a war for no discernible reason. They can viciously assault a planet, and then send a blockade runner to another enemy planet that has been quarantined in order to deliver a cure. At the end of the third book, Sergey realizes that the Fangs' primary guiding principle is.
 * Casual Interstellar Travel - hyperjumps are only possible to known coordinates. This is achieved by every populated planet having a Seeder temple that gives the indigenous civilization the hyperspace coordinates of other planets in the "network". Earth, normally, cannot be reached via hyperspace, as it lacks a Seeder temple, although there have been stories of ships stumbling on the planet by accident, usually while performing a Blind Jump.
 * Earthshattering Kaboom - a quark bomb is a transparent cube about 2 meters in length. It explodes immediately upon construction, but the quark fission process is slowed down to a crawl. If the container is broken, then the fission process resumes in full force, breaking down any form of matter in the vicinity. A quark bomb is fully capable of destroying a planet in a matter of hours. Once started, the process is irreversible and cannot be stopped. The quark fission process can even spread to another planet by way of tiny meteorites or dust particles from the dead world. Using such a weapon is considered an atrocity in the galactic community. Teleporting a quark bomb renders it inert.
 * Everything's Better With Princesses - Princess Terri of Tar is a beautiful young woman who meets Sergey several years before the main events of the book when she visits Earth. He defends her against a group of thugs, and she asks him to be her champion when the time comes, leaving him a ring. Several years later, she uses the ring to teleport him to Tar, when her planet is threatened. They later fall in love and marry. Unlike your typical princess, Terri is more than capable of handling herself, and the thugs were just a test for Sergey.
 * Free-Love Future - On the 22nd century Earth, it's stated that at least some groups adhere to this idea. When the protagonist is disgusted by seeing a wild threesome in the woods (when at least one of the participants is clearly underage by the protagonist's standards), an elderly man points out that the kid is considered an adult by their laws, having passed the test on self-sufficiency. Additionally, this society seems to take an all-or-nothing approach to freedom. Either you're free to do anything (including an orgy in the woods with teenagers) or you can't have any rights. On the other hand, it's also shown that the institution of marriage hasn't disappeared. The assumption is that you can have married couples coexisting with Ethical Sluts without any issues.
 * Human Alien - this is actually explained by most known habitable worlds being seeded by Precursors aptly called the Seeders. Some aliens are virtually indistinguishable from humans, while others have grey skin, vampire fangs, etc.
 * Played straight with the Fangs, who are from another galaxy and whose planet has not been visited by the Seeders.
 * Inertial Dampening - gravity compensators are utilized in spacecraft, aircraft, and Space Elevators. They look like black spheres that contract when absorbing g-forces. Unlike "traditional" inertial dampers in fiction, these require the energy to go somewhere, so the crew must suffer increased gravity for weeks or months as payback. They can be jettisoned, but this creates a navigational hazard due to the creation of a new gravity field. They are also very expensive. Gravity compensators are a Seeder technology.
 * Jerk With a Heart of Gold - Sergey, the protagonist, is a bully at the beginning of the first novel. At a party, he steals his friend's date and pretty much forces her to have sex with him (she was interested, but he didn't feel like "wasting" time wooing her; he simply ordered her to undress, the way he would order a private to "drop and give him 20" back in his army days). After ending up on planet Tar and asked to rescue Princess Terri, his personality changes a little, and, by the next two books, he drops his "jerk" shell, for the most part.
 * Mental Time Travel - after arriving on Tar, Sergey is given two pencil-shaped crystals that are supposed to be Seeder artifacts with unknown properties. They turn out to be devices for throwing the user's consciousness back in time. Interestingly, when Sergey uses one and goes back a few hours, he no longer has the artifact.
 * Our Vampires Are Different - the Palians are a race of blood-drinking Human Aliens, whose fangs, pale skin, and sensitivity to light from yellow dwarf stars became the origin of the vampire myths on Earth.
 * Precursors - the Seeders were responsible for spreading life spores on all known inhabited worlds . Nobody knows what they looked like, as they disappeared long ago. They left behind numerous artifacts as well as a Temple on each planet, except Earth, that provides hyperspace coordinates to all other Temples, allowing interstellar travel. Because Earth lacks a Temple, it is cut out from the galactic community. As such, many aliens think that Earthlings have somehow wronged the Seeders and are thus cursed. At the end of the second book, it is revealed that.
 * Sharpened to A Single Atom - the planar (or monoatomic) swords have a blade that is only one atom thick. Because of this, it can cut through any known material with little effort. Every strike or even a wave dulls the blade. The blade can be re-sharpened with a button on the hilt but only about 1500 times. When two planar swords collide, one will invariably cut through the other. This depends on the angle of impact as well as the sharpness of each blade. This makes Blade Locks impossible. One wrong move can leave a fighter defenseless, making technique and timing extremely important in any duel. When not in use, the sword is held in a special magnetic holster. A wound from a planar sword is nearly painless and will heal within seconds if undisturbed. Due to the common use of neutralizing fields, monoatomic swords are the most reliable handheld weapons in the galaxy.
 * Being a Combat Pragmatist, the protagonist desides to improve his chances by designing several new weapons, including a planar disc (a steel disc with monoatomic shards glued to the rim), which is capable of easily decapitating the target. There are also smaller, shuriken-like versions. He also later builds an airgun that fires these planar shurikens suspended in a magnetic field. Their design is similar to hollow-point bullets in that they change direction after entering the body, shredding the insides. Everybody else thinks his methods are horrible and prefers Honor Before Reason.
 * Teleporters and Transporters - teleportation is possible to any known planet, even Earth, despite Earth being unreachable via hyperspace. As such, aliens have been visiting Earth for centuries by using this method, sometimes resulting in myths being formed. Teleportation is a costly technology and cannot be used for commercial or military purposes, as only about 70 metric ton can be transported at once. All high-tech weapons are rendered inert by the process.