Builder's Manual · Chapter 1

What Isekai Lite Is

Isekai Lite is a 2d6 system built to be run by an AI Game Master and extended by hand. Every design decision serves one of four pillars. Hold to them and anything you add will fit.

Small numbers. The core roll is 2d6 + stat against Difficulties of 6, 8, 10, 12, and 14. Starting Health is 5. Weapon damage runs 1 to 4. Ability damage of 1 or 2 is normal and 6+ is apex content. Flat bonuses are +1 or +2 to a narrow named thing, never "+2 to all rolls". On a 2d6 curve every +1 is worth roughly 12 percent, so a bonus that looks polite is already strong. When in doubt, write the smaller number.

Three stats. Might, Wit, and Finesse cover everything. Raw values run -1 to +5, and creation spreads +2, +1, +0. There is no fourth stat hiding anywhere. Skills, saves, attacks, Initiative, and Save DCs all resolve to one of the three. New content must hook into them, never around them.

Gear that computes. Every piece of gear carries numeric bonus fields the character sheet sums automatically. Prose effects exist, but they are bounded, tiered by rarity, and never a raw stat grant. If a designer cannot express most of an item in numbers, the item is fighting the system.

XP everywhere. XP is the single advancement currency. Stats, Health, pools, and all four ability types are priced in it. There are no levels, no classes, and no milestone unlocks. This keeps the AI GM's job simple. When a player asks what they can afford, every answer is a number.

Two structural rules protect the AI GM. First, no reactions. Nothing in this system triggers on someone else's turn, so never write content that does. Second, the sheet does the math. Bonuses from species, archetypes, General Abilities, and the eleven gear slots land in computed totals that the GM reads directly. Content you write feeds those totals through its numeric fields. Keep the numbers in the fields and the flavor in the prose, and the machine stays honest.

Manual updated Aug 19, 2026.

Isekai Adventure

[Isekai Adventure System - Adventure Mode] Go from Earth to a fantasy world just by saying "Log in." The System is your new guide. Welcome to an isekai where the summoned come from Earth and the door swings both ways. The System chose you. Log in and you stand in Kavrix, a realm of kingdoms, guilds, a Dark Lord, a Demon Lord and a Lich King. Log out and you are back on Earth with every power you earned still humming in your hands. Governments are watching. Godlike Players have already picked sides. Will you be the hero of two worlds, or their villain?

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@Pollution

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CreatedAug 19, 2026

UpdatedAug 20, 2026

Earth x Kavrix

Log in to a brand new world.

Go from Earth to a fantasy world just by saying "Log in." The System is your new guide. Welcome to an isekai where the summoned come from Earth and the door swings both ways. The System chose you. Log in and you stand in Kavrix, a realm of kingdoms, guilds, a Dark Lord, a Demon Lord and a Lich King. Log out and you are back on Earth with every power you earned still humming in your hands. Governments are watching. Godlike Players have already picked sides. Will you be the hero of two worlds, or their villain?

Author's note

Thanks for stepping in to Isekai Online. I hope you enjoy the journey as much as I enjoyed making it.

This game runs on the Isekai Adventure system, based on Craft Lite.

Inside the World