Library Of Ruina is Project Moon's 2021 deck battler, where you run a Library that mails out invitations, fights the Guests who accept, and turns the losers into Books. Every librarian is defined by one Key Page, which fixes HP, Stagger Resist, Speed and the Slash, Pierce and Blunt resistance columns, plus a deck of exactly 9 Combat Pages. Fights resolve as clashes: both sides roll dice at each other, the higher roll wins and the loser's die is destroyed, so damage is something you win rather than something you spend. Books drop the pages that build the next deck, which means the difficulty curve is assembled out of whatever you beat last.
These tips go beyond the basics. They're the strategies experienced players use to play more efficiently, the hidden mechanics most people miss, and the optimizations that compound over a full playthrough. If you're just starting, check our beginner's guide first.
Essential Tips
1. Open the guest's Key Page before you build
Open the guest's Key Page before you build. The Slash, Pierce and Blunt columns run Ineffective 0.25x, Endured 0.5x, Normal 1x, Weak 1.5x and Fatal 2x, and the stagger table is separate from the HP table, so a fight can be won on stagger with damage types that barely scratch health.
2. Redirecting is free and it is the strongest button in the game
Redirecting is free and it is the strongest button in the game. Pointing a librarian at whichever enemy die would otherwise hit unopposed converts a one-sided attack into a clash, and a clash you lose still destroys nothing except one die.
3. Emotion Points come from clashing at all, not from winning
Emotion Points come from clashing at all, not from winning. Losing a clash still pays 1 point, and rolling either the maximum or the minimum on a die pays another, so a scrappy scene often levels your whole floor faster than a clean one.
4. Emotion Level 4 grants an extra dice slot and every level refills Light, so the fourth level is worth more than the first three combined
Emotion Level 4 grants an extra dice slot and every level refills Light, so the fourth level is worth more than the first three combined. Plan the fight so the level up lands before the guest's own escalation, not after it.
5. Defeating or staggering a target refunds 1 Light
Defeating or staggering a target refunds 1 Light. Finishing a nearly dead guest with a cost 1 page is a net gain, which is why cheap closers earn deck slots over expensive ones that look stronger on paper.
6. Decks are exactly 9 Combat Pages per librarian, and pages are drawn, not summoned on demand
Decks are exactly 9 Combat Pages per librarian, and pages are drawn, not summoned on demand. Three copies of the page the build depends on is normally correct, because two copies in nine cards will not show up when the plan needs it.
7. Bleed and Burn decay differently
Bleed and Burn decay differently. Bleed loses a third rounded up each time an offensive die is used, while Burn ticks and loses a third at the end of the scene, so Bleed rewards attacking guests and Burn rewards defensive ones.
8. Paralysis has a floor of 1, so it never removes a die outright
Paralysis has a floor of 1, so it never removes a die outright. Use it on the guest's single biggest die rather than spreading it, because cutting a 10 to a 7 changes clash odds far more than trimming three small dice.
9. Books are invitations, which means the order of the campaign is your choice
Books are invitations, which means the order of the campaign is your choice. Farm one reception you already beat to print spare pages before scheduling the guest that keeps wiping the floor.
10. Floor of Natural Sciences needs every lower floor at Realization Level 4, so ignoring Floor Realization for a stretch will lock you out of the mid-game roster even if your combat is fine
Floor of Natural Sciences needs every lower floor at Realization Level 4, so ignoring Floor Realization for a stretch will lock you out of the mid-game roster even if your combat is fine.
Advanced Strategies
Build Optimization
The difference between an average build and an optimized one is massive. See our builds guide for full breakdowns.
For Floor of General Works (A-Tier):
- Focus on Clashes and speed dice combinations for maximum output.
- Core gear: Slash dice
- Stat priority: Offensive stats first
For Floor of History (A-Tier):
- Versatile approach that handles any situation.
- Core gear: Pierce dice
- Stat priority: Balanced stats
Mechanic Interactions
Understanding how Library Of Ruina's systems interact is where the real optimization lives. Our combat guide covers this in detail.
Clashes and speed dice + Light and page cost: At the start of each scene every character rolls speed dice, and those results set both turn order and who can be targeted. Combined with Light and page cost, light pays for combat pages.
Stagger Resist and damage types + Emotion Level: Every hit reduces HP and Stagger Resist on separate tracks with separate resistance tables. When paired with Emotion Level, emotion starts at 0 in a reception and climbs to a cap set by floor level for librarians and chapter rank for guests, up to 5.
Books and Reception invitations scaling: Beating a guest drops their Book, which you burn at the desk for Key Pages and Combat Pages. Books double as invitations, so you pick which guest arrives next instead of being pushed down a fixed track. That is the loop: the pages you strip off one reception are the pages you need to survive the one you deliberately schedule after it.
Equipment Efficiency
| Equipment | Best Use Case | Why |
|---|---|---|
| Slash dice | Bleed decks, and any guest whose Key Page reads Weak at 1.5x or Fatal at 2x in the Slash column. | One of the three offensive damage types, and the one most Bleed pages are attached to. |
| Pierce dice | Guests who are Endured at 0.5x against Slash but Normal or worse against Pierce. | The second offensive type, tracked on its own resistance row for both HP and stagger. |
| Blunt dice | Hands that stay full, and stagger-focused plans where the Blunt row is the weak one. | The third offensive type. |
| A Zwei Fixer's Page | Mid-game floors that need a durable body while the good Combat Pages are still being printed. | An Urban Legend rank Key Page, sitting in the same tier as A Stray Dog's Page and the Grade 8 Fixer pages. |
| A Grade 7 Fixer, Page 1 | Replacing default Assistant Librarian pages once Urban Legend receptions start dropping Books faster than you can burn them. | One rung above the Grade 8 Fixer pages, on the City's fixer scale where Grade 9 is the bottom and Grade 1 the top. |
Location Efficiency
Canard (Chapter 1, one floor available): The opening rank, fought entirely from the Floor of General Works. Finishing episode 3 of Yun's Office opens the Floor of History, and clearing the Hook Office reception opens the Floor of Technological Sciences.
Urban Myth (Chapters 2 to 3, two or three floors): The second rank, where guests start bringing passives worth reading. Episode 1 of Streetlight Office opens the Floor of Literature, giving you three floors to rotate receptions between.
Urban Legend (Mid campaign, four floors): Reaching this rank unlocks the Floor of Art outright. This is the first tier where the Key Page pool jumps in quality, and where default Assistant Librarian pages stop being acceptable.
Urban Plague (Late campaign, six to eight floors): Guests here punish sloppy resistance checks. Finishing the Shi Association reception opens the Floor of Language, and clearing the Puppets reception after that opens the Floor of Social Sciences.
Urban Nightmare (Endgame, all lower floors at high Realization): The rank before Star of the City, which is itself the gate on the Floor of Philosophy. Clearing a single Star of the City reception then opens the Floor of Religion, leaving Impuritas Civitatis as the last tier.
Mistakes Even Veterans Make
- Building a deck around damage types the guest resists at 0. 5x or 0.25x
- Letting enemy dice go unclashed because redirecting looked risky.
- Running one copy of the key Combat Page in a 9 card deck.
- Spending Light on cost 4 pages while a cost 1 finisher would have refunded it.
- Ignoring Floor Realization until the Floor of Natural Sciences requirement blocks progress.
Pro Quick Tips
- Open the guest's Key Page before you build. The Slash, Pierce and Blunt columns run Ineffective 0.25x, Endured 0.5x, Normal 1x, Weak 1.5x and Fatal 2x, and the stagger table is separate from the HP table, so a fight can be won on stagger with damage types that barely scratch health.
- Redirecting is free and it is the strongest button in the game. Pointing a librarian at whichever enemy die would otherwise hit unopposed converts a one-sided attack into a clash, and a clash you lose still destroys nothing except one die.
- Emotion Points come from clashing at all, not from winning. Losing a clash still pays 1 point, and rolling either the maximum or the minimum on a die pays another, so a scrappy scene often levels your whole floor faster than a clean one.
- Start with Floor of History, switch to Floor of General Works when ready
- Invest in Slash dice above everything else
- Clear areas in order: Canard → Urban Myth → Urban Legend → Urban Plague → Urban Nightmare. See our maps guide
- Clashes and speed dice + Light and page cost together are stronger than either alone
More Library Of Ruina Guides
- Library Of Ruina Library Of Ruina Overview
- Library Of Ruina Best Builds
- Library Of Ruina Tier List
- Library Of Ruina Walkthrough
- Library Of Ruina Beginner's Guide
- Library Of Ruina Weapons Guide
- Library Of Ruina Combat Guide
- Library Of Ruina Boss Guide
- Library Of Ruina Maps & Locations
- Library Of Ruina Crafting Guide
- Library Of Ruina Classes & Characters
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