Library of Ruina is an indie deck-building turn-based role-playing game developed and published by South Korean studio Project Moon.

Initially released for Windows and Xbox One on August 10, 2021, it is a direct sequel to the 2018 PC game Lobotomy Corporation.

Another light novel, Leviathan,[2] was illustrated as a comic, taking place between Library of Ruina's true ending and the start of Limbus Company.

The titular library is split up into ten unlockable floors for fighting against enemies, or "guests", in battles known as "receptions".

Cutscenes about guests and miscellaneous discussions are shown once a reception starts and ends, typically delivered through conversations between two library residents, Angela and Roland.

Emotion level is a mechanic that raises whenever a character wins or loses a clash, or when their dice rolls its maximum or minimum value.

The City is governed by the a reclusive organization known as the Head, while the Nests are run by Wings, mega-corporations that harness powerful technologies known as Singularities.

A mysterious Fixer known as Argalia recruits various characters for an unknown cause, culminating in them breaking into the Library, scattering to the ten floors to claim the Light for their greatest performance that will overturn the City.

Angela, burdened by the guilt of killing her friends and the city folk, continues her aimless destruction for years before letting a nameless follower end her life.

If all Floor realizations have been completed and Angela and Roland choose to forgive each other, Angela will release the culminated Light and resurrect all lives the Library has taken, kickstarting the Kether floor realization facing against Carmen, founder of Lobotomy Corporation's Seed of Light and actual mastermind behind the Distortion phenomenon.

Facing great retaliation from Roland and fellow librarians Gebura and Binah, the Head agents decide to instead stick to their main plan and expel the Library into the Outskirts.

For Library of Ruina, Mili made a mini album, To Kill A Living Book,[8] with seven out of the eight songs being tailored to specific characters.

[19] Xbox Hub writer Richard Barker praised the compelling nature of the game's narrative while criticizing its unclear battle mechanics.

[20] On consoles, the game was generally positively noted for its narrative and voice acting, but was criticized for its performance issues, confusing gameplay and sluggish interface.

Shaun Musgrave, in his review on TouchArcade, said the Nintendo Switch version has "fantastic characters and sublime music" with a new Japanese voiceover option.

He found the console version's stability issues a downgrade from the PC counterpart, which he noted was already poorly optimized, and commented its text size is too small to be playable.

[15] Charlie Wacholz of Nintendo Life gave it a negative review, criticizing confusing gameplay, clunky menus, and performance issues.

He found the game difficult to play in longer sessions due to its text being almost illegible on screen, and compare its trial-and-error gameplay to "a mild bout of Stockholm Syndrome".

[14] Kazuma Hashimoto from Siliconera left a mixed review, calling its voice acting "top notch" and enjoying its turn-based battle system for its complexity.

However, he noted the Nintendo Switch version suffers from slapdash interface, whose font size is too cramped and small to read, especially in handheld mode.