Quite possibly the most important section of Korrinthian lore; having read this, one would know enough about the Krii to possess a general understanding of them as a whole.
I just finished fluffing it to try and make it a generally nice read; fair warning: its roughly 33,000 words and should take about 3 or so hours to read.

Here is a synopsis if you need to be sold on the idea first:

This is a chronicle of the history of the Krii, an advanced race of felid-humanoids from the planet Korrin; an earth-sized planet located in the Ethereum galaxy. Korrin is a lush, temperate world with a challenging environment full of gigantic plants, animals and a naturally radioactive biosphere.

-Early Ages-

-Paleolithic Age (60,000 PDK)
The Krii split into two main groups—Temperate and Tropical. Early societies were hunter-gatherers, with migratory tropical tribes and more stationary temperate tribes. In this era it is discussed how the Krii produced early shelters, tool use, and how burial practices emerged.

-Neolithic Age (30,000 PDK)
A time marked by the development of agriculture, permanent settlements, pottery, and notably, the early discovery of glassmaking which happened thousands of years ahead of human cultures. In this section the Krii migrated and evolved into multiple distinct subgroups; adapting to Korrin's mangroves, swamps, forests, plains, and alpine regions.

-Bronze Age & Social Upheaval-

-Bronze Age (15,000 PDK)
Expansion led to resource conflicts, the rise of the powerful desert communities, and the mining of salt, which they used as an early currency; as well as copper, and tin which resulted in viciously competitive monarchies and a littany of early wars.
During this time their population boomed, resulting in a plague which reshaped their society.

-Immortal Gene (10,500 PDK)
A bacterial epidemic led to a symbiotic genetic mutation, vastly extending lifespans but reducing birth rates. Triggering the mass enslavement of males for reproductive purposes.

-The Peoples Revolution (10,000 PDK)
Centuries of oppression led to a revolution, overthrowing the monarchies and establishing a clan-based governance led by matriarchs. Males were freed, and a system of consensus-based rule emerged.

-Technological & Social Evolution-

-Iron and Aluminum Age (9,000 PDK)
Peace and cooperation spurred technological advances, including steam power and deeper mining. The discovery of aluminum deposits from an ancient crash site revolutionized engineering.

-Order of the Mystics (8,200 PDK)
A techno-mystical religion arose, blending faith with scientific progress, centered on the concept of the universe as a vast machine.

-Industrial Revolution (8,500 PDK)
Discovery of oil led to rapid industrialization, urbanization, and eventual environmental decline.

-Crisis & Transformation-

-Environmental Collapse (7,900 PDK)
Pollution and complacency threatened planetary survival. The construction of ALPHA, (a superintelligent AI) was initiated to devise solutions to their problems.

-The Redemption Project (7,800 PDK)
ALPHA led a planet-wide terraforming effort, reorganizing society around environmental restoration and cybernetic enhancement. Subordinate AIs were created to optimize efficiency and guide the Krii through a new era of techno-tribalism.

-Space Age & Galactic Integration-

-Dawn of the Korrinthian Empire (5,100 PDK)
Population growth and resource demand prompted the push for space travel. The Krii, guided by ALPHA and its new AI children, began interstellar exploration and colonization.

-Discovery of the Psyben (4,000 PDK)
First contact with the Psyben, a fungal hive-mind species on the moon Tā’liā, led to a symbiotic partnership and technological evolution.

-Vivarium Ships & Golden Age (3,800–2,000 PDK)
Creation of self-sustaining starships enabled expansion throughout the solar system, ushering in a golden age of peace and prosperity.

-Cataclysm & Migration-

-Epoch Event:
A black hole threatened their home system, forcing a massive evacuation. The Krii and Psyben migrated across space, enduring famine, war, and the loss of their AI pantheon and leadership.

-Resource War & The Divine Connection:
Infighting decimated the population as their machines continued to fail resulting in mass starvation. Survivors developed technopathic abilities, allowing direct communication and control over machines, which revitalized their fleet.

New Beginnings & Galactic Politics:

-Galactic Council (260 ADK)
The Krii were welcomed by the Interspecies Galactic Union, receiving territory and a new home world, Korrinthia. They rebuilt their society, integrated with other races, and adapted to new technologies and magical phenomena.

-Rise of Empress Āmèlā (650 ADK)
Political strife over council representation led to the rise of a new Empress, consolidating leadership and restoring order.

-Military & Intergalactic Relations (880–1,200 ADK):
The Krii established a formidable military under the new ASI "Omega", navigating numerous diplomatic challenges, and encountering the Milkyway races (MWR), leading to new alliances and cultural exchanges.

-Present Day (1,274 ADK)
The Krii are active participants in a galactic effort of exploration and research, collaborating with the other species to uncover ancient secrets and advance technology after finding the remnants of a galactic precursor species.

For more lore see:
https://www.furaffinity.net/view/62471857/