Giant Koi | World Anvil - Isekai Codex

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Giant Koi

Giant Fish of Lake Idryl

Beneath the cool blue waves of the lake lurks a world that few know and even fewer enter. The lack of knowledge of the true depth scares even the most seaworthy, the creatures below the surface a mystery. An innate fear of the water permeates life around the idyllic shores of Lake Idryl, but even so, delicate creatures call the waters home, ones that bring luck and peace to those who must travel the waves by ship. As the depths lurk in the shadows, the shimmering white and gold scales of these behemoths give some calm to the storm in sailors' hearts.   Giant Koi are one of the most common creatures found beneath the waves of Lake Idryl, although the true numbers of the population are unknown. Their scales vary widely in color, often white and gold, but can include shades of orange and black as well. Considered to be the largest freshwater fish in the world, these fish can only be found in one place in the world and are very difficult to confuse with any other creature.   Sailors see these creatures as a blessing or a luck charm when they grace the surface of the lake. Only appearing during daylight hours, the presence of the koi means safe passage across the lake, no matter the vessel or its size. While the rest of the lake's inhabitants are a mystery, it has been known for centuries that as long as a Giant Koi is in sight, the more horrific creatures of the depths will not bother anyone who enters the water.  

Basic Information

Giant Koi Variations
It is believed that Giant Koi that live deeper within Lake Idryl will become darker in color, their white scales changing to black. These fish will also grow longer fins and tails that can be used to shroud themselves in the darkness. Scholars are unsure how true this information is as it is difficult to study most creatures in the lake.


Giant Koi are large fish that can range anywhere from two feet long in adolescence to nearly fifteen feet long in their older years. These creatures can weigh upwards of multiple tons depending on their length. It is believed that no larger creature exists in Lake Idryl other than the Giant Koi.   While considered to normally be white and gold or orange in color, the scales of the koi range widely in color, often including shades of black, gray, orange, white, and gold. It is believed this wide range of colors denotes the depth at which the fish lives, but this is not something that Scholars have been able to completely confirm.   The Giant Koi of Lake Idryl are unmistakable creatures, mostly due to their color but also the gentleness with which they rise to the surface to feed and allow those on the water to pet them. Some sailors have taken to calling the large fish "sea puppies" because of their demeanor and willingness to take food from people's hands.  


While the true size of the population is unknown, these creatures are considered a protected species by the people who live around the lake. Titles such as Koi Catcher are meant to honor those who have seen the largest fish and have fed it, while those that would harm the creatures are very swiftly dealt with through the judicial systems of the area in which they were caught. Even faraway kingdoms, such as the Elven Kingdom and Human Empire, recognize the harm of these fish as a great offense.
Giant Koi
Giant Koi are considered to be one of the largest marine animals that can be found in freshwater throughout Isekai. These creatures grow to massive sizes due to the abundant plant life in Lake Idryl and have been known to live for decades beyond what smaller koi do.
Scientific Name
Fae carpio
Over 200 years
Average Weight
Up to 8 tons
Average Length
Up to 15 feet
Group Name
Lake of Giant Koi
Geographic Distribution


Author's Notes

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Dec 28, 2023 23:31 by Dr Emily Vair-Turnbull

They are so large! I love them. <3

Emy x   Etrea | Vazdimet
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