Spoiler! Spoiler! Spoiler!
There are only two systems, along with several system windows. The systems are connected and not connected at the same time.
The main system window shows everything Lucius currently has access to across both systems at once. There is also an option, like in a game, to transfer something directly onto the character model, the way Lucius did when forming his aether core or during his experiment with the Four-Sided Physique.
The Connection System makes it possible to link with someone and receive back ten times more, or upgrade something to the next rank. It also has a talent panel where you can increase or decrease the talent of the person you are linked to, although you cannot lower a talent below what it originally was. It also shows all talented people within a one-kilometer radius.
As for the ranks, advancing to a higher rank brings a major refinement that removes every flaw and imperfection. It was like that with the clothes Lucius knitted. At first, although the clothes looked fairly decent, they still had shortcomings: loose threads sticking out, uneven stitching, and gaps between the sleeping bag that served as the inner padding and the beast hide stretched over the outside of the garment. But after being upgraded to Rank 6, the clothes looked as if someone had created them out of nothing, rather than knitting them from a sleeping bag and beast hide.
Everything is returned in the form of points: pain adaptation points, intelligence points, body points, and even things that can physically appear in your hands, like a kettle or mugs.
If you choose aether, you receive not only pure aether into the core, but also a fragment of understanding about aether. The same applies to mana.
When obtaining a God Rune, several improvements happen at once: general understanding of aether, the quantity and quality of aether, aether control, and understanding of a specific aether edict depending on the God Rune.
The Wealth-Doubling System makes it possible to place something into it and receive another identical item after 24 hours. There are no restrictions. It can duplicate a God Rune, a talent, or the Four-sided physique+.
The system can also completely butcher animal corpses, though with some percentage loss from the total.
Oh, and one more thing: the system does not give hints unless you stumble upon them yourself. In Chapter 36, when Lucius tried to raise his Intelligence rank to 11, the system reacted. If he had not done that, the system would have stayed silent. The same goes for butchering a corpse: while holding it in his hands and thinking about what to do with it, the system revealed another function.
There are also ranks and realms in the system, the limits of which Lucius does not know, because a rank only appears after he reaches it.
So:
1st Realm: Rank 1 to Rank 6
2nd Realm: Rank 7 to Rank 10
3rd Realm: Rank 11 to Rank 14
4th Realm: Rank 15
5th Realm: Rank 16 (peak of God Runes and the Realm of Fate)
6th Realm: Rank 17 (I'll explain later, but that power is horrifying.)
Without the system, Rank 17 is the absolute peak. No one could ever reach Rank 18 except Lucius.
7th Realm: Rank 18 (absolute peak)
x4 between ranks
x20 between realms up to Rank 14
x100 between Rank 14 and Rank 15
x270 between Rank 15 and Rank 16
x1000 between Rank 16 and Rank 17
x way too much to write at Rank 18
System Updates
To update the system and advance to Rank 11, all characteristics must be brought to Rank 10, after which they must all be advanced to Rank 11 in a single step. The exception is the soul.
For the second update and advancement to Rank 15, the soul and at least 5 God Runes must be Rank 14. For the third update and unlocking all characteristics at Rank 16, the soul must be advanced to Rank 16.
For the fourth update, it is necessary to absorb part of the Core of Fate. I will repeat: the soul is not restricted by system ranks. If there is an opportunity, it can be raised straight to Rank 17 immediately.
As for the systems, I think that briefly explains everything.
[Body: Four-Sided Physique (Seventh Rank), Eighth Rank]
[Soul: Half Otherworldly, Eleventh Rank]
[Intelligence: Tenth Rank]
[Energy: Second-Layer Aether Core (Eighth Rank); Eighth-Rank Aether Channels]
[Pain Adaptation: Tenth Rank]
[God Runes: God Rune of Theft (Eleventh Rank), God Rune - God Step (Eleventh Rank), God Rune of Destruction (Twelfth Rank), God Rune of Aroa's Requiem (Thirteenth Rank)]
[Echoes:]
[Rank 14 God Rune of Destruction x21]
[Rank 13 God Rune of Aroa's Requiem x5, God Rune of Destruction x21, God Rune - God Step x21]
[Rank 12 God Rune of Destruction x21, God Rune - God Step x21]
[Rank 11 God Rune of Theft x3, God Rune - God Step x21]
[Rank 11 Fighter Talent x21]
[Rank 11 Keystone x21]
[Rank 10 World Seed x21]
[Rank 10 Aether Crystal x21]
[Rank 8 Weapon x21]
[Rank 9 Four-Sided Physique+ x21]
[Rank 7 Four-Sided Physique x29]
[Rank 7 Aether Core x29]
[Rank 7 Aether Channels x30]
[Rank 7 Mental Connection x20]
[Rank 7 Extradimensional Storage Rune x29]
[Rank 7 Aether Fruit x21]
[Rank 6 Turquoise Cloak x21]
[Rank 7 Black Sword x21]
[Rank 6 Clothing Set x21]
[Rank 6 Pseudo-Artifact of Flight x3]
[Rank 7 Pseudo-Artifact of Healing x3]
[Rank 7 Pseudo-Artifact of Fire x3]
[Rank 7 Pseudo-Artifact of Bone Bird x3]
[Rank 7 Pseudo-Artifact of Bone Reinforcement x1]
[Rank 6 Pseudo-Artifact of Bone Reinforcement x3]
[Rank 7 Pseudo-Artifact of Bone Compression x3]
[Rank 7 Pseudo-Artifact of Bone Arrow x3]
[Rank 7 Pseudo-Artifact of Bone Shield x3]
[Rank 7 Pseudo-Artifact of Bone Mace x3]
[Rank 7 Pseudo-Artifact of Bone Spikes x3]
[And a huge amount of miscellaneous items in the form of food, trees and minerals from different zones, water, hides, monster parts, basic necessities, thread, and a lot more junk that Lucius gathered of various ranks, though none above Rank 5.]
[Also, many of the items here are now at a lower rank than their original rank. For example, the aether fruit was originally Rank 3, and only the very first one was Rank 4, but after many upgrades it became Rank 7.]
System Mail currently contains:
124 thousand aether points from two uhnads.
238 thousand aether points from Arthur.
113 thousand aether points from Regis.
46 thousand intelligence points.
97 thousand constitution points.
8 thousand pain adaptation points.
The boring part is over. Now for the main question of the fanfic: who is the FL, or is it a harem?
The answer: the Horned Mommy Caera. Caera will grab Lucius by the dick and will not let him run away to his own world forever.