One of the most thrilling and rewarding fights in Bloodstained: Ritual of the Night is the optional boss battle against OD, the enigmatic librarian of the Livre Ex Machina. This isn’t your typical optional encounter—OD channels full-blown Alucard energy from Symphony of the Night, complete with bat transformations, time-stopping powers, and devastating swordplay. He’s powerful, relentless, and utterly deserving of the “secret boss” title.

If you’re gearing up to take him on, here’s everything you need to know, including how to unlock the fight, how to survive it, and how to turn the battle to your advantage.

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How to Unlock the Fight with OD

To face OD, you must have at least one book checked out from his library. It doesn’t matter how many—one is enough to trigger his wrath. Head to the Ice Tomb, and you’ll find him waiting. You don’t need to worry about losing his services after the fight; OD remains available as a vendor post-battle, and in fact, he rewards you for defeating him.

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Preparation: Loadout and Gear

OD is a massive difficulty spike. This is one of the hardest fights in the game, and your setup matters immensely. Here’s a sample build that helped turn the tide:

• Weapon: Durandal
• Head: Ancient Tiara
• Body Armor: Coronation Gown
• Accessories: Silver Power Ring + Traverse Ring
• Scarf: Talisman Scarf

With this setup, you’re geared for durability, speed, and consistent damage output. Even so, OD can easily shave off hundreds of HP in a flash, so be ready for a slugfest.

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Top Strategy: Invert the Room

The fight takes place in a special room that works beautifully when inverted. Flipping the room upside down gives you a much stronger position against OD’s arsenal of flame pillars, slashing strikes, and magical projectiles. It’s disorienting at first, but it completely changes the rhythm of the encounter—and once you adapt, you’ll find it easier to dodge and land hits.

OD’s movements can still be unpredictable even upside down. He jumps toward you and slashes, and he’ll summon flame pillars that reach from floor to ceiling. You’ll need to keep moving and anticipate his positioning constantly.

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Danger Zones: Mist, Bat, and Time Stop

As OD’s health drops, he begins using classic Dracula transformations:

• Mist: He becomes untouchable and repositioned instantly.
• Bat: This is his deadliest form. He will divebomb you with a brutal wing crush move, often dealing 200–500 damage per hit. Stay airborne and double jump as he swoops to avoid catastrophic losses.
• Wolf: A lunge attack that’s less dangerous if you’re upside down, but still worth watching for.

Possibly his most iconic move is Time Stop. When triggered, you’ll be completely frozen while OD acts freely. You can’t resist it—there’s no counter. This phase is about damage control: limit how close you are to him, and try to predict when he’ll trigger it to stay out of reach.

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Battle Tips: Pattern Recognition and Patience

Recognizing when OD is about to transform is crucial. Once you see him disappear into mist, prepare to double jump or get into a safer part of the arena. Most of his bat attacks are telegraphed just barely in time to react—but you’ll need sharp timing and a steady rhythm to survive.

Another key moment is identifying when he begins cycling all his abilities rapidly. This means he’s around half health. Once he starts chaining transformations, you’re nearing the end—but also the most dangerous part of the fight. Stay disciplined and don’t get greedy with your attacks.

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Victory Rewards and Post-Fight Benefits

Once you bring OD down, you don’t lose access to him as a vendor. Instead, he respects your strength and becomes even more useful. He says you’ve bested him and now “command him.” What this means in gameplay terms is: you can check out all 21 books at once if you’ve unlocked the full library by completing the 8-bit Nightmare and other milestones.

This bonus is game-changing. Having 21 buffs active at once can turn you into an unstoppable machine—a perfect prep state for the final boss and post-game content.

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Final Thoughts

OD is everything an optional boss should be: brutally difficult, thematically rich, and hugely rewarding. Between the fierce transformations, the elegant swordplay, and that wonderful Alucard homage, this fight stands tall as one of the best in Bloodstained. Flip the battlefield, study his tells, and come prepared. He’s not just a librarian—he’s the final exam.

Once you’ve passed it, you’ll walk away with power, pride, and a personal library that would make Dracula jealous.

Good luck—and may your wing crushes always miss.