Sleeping Bag of a Bygone Day

Overview

Enemy

Sleeping Bag of a Bygone Day (T-03-16-15) is a TETH-class Abnormality that is fought on Station 4 of Line 5: Merry Go Round.

It can also be encountered in the Mirror Dungeon through Abnormality events.

It is the source of the E.G.O Thoracalgia.

Appearance

Sleeping Bag of a Bygone Day is comprised of two distinct parts.

The first is a large skeletal entity with an elongated ribcage, the bottom of which juts forward to form a red, bony spiral. The top of the ribcage is connected to a black spinal cord, topped by a massive, completely black human skull glowing with red light from its orifices. Blood constantly leaks from the skull's eye sockets.

The second part is a dark ghostlike humanoid entity with red eyes wearing a T-shirt and shorts, standing within the cavity of the skeleton's ribcage.

Observation Logs

Log Writer: Outis

Level 1Level 2Level 3

Performing the post-mortem report as ordered by the Executive Manager.

The entity was encountered around 1040 hours today.

It assumes the form of a gigantic skull, which explains our ease of identifying this enemy.

(Heavy breathing) The size of the skull is rather intimidating, and it features what appears to be a support of sorts that looks like a spine surrounded by ribs.

Though I may be making a rather large leap in logic here… (Heavy breathing) it can be assumed that the rest of its shape is not so dissimilar to that of human bone structure.

Initially, we had attempted to exploit the equivalents of the usual weaknesses identified on human bodies based on this similarity. However…

… once we observed its extendable spine (Heavy breathing) and morphing of its ribs into arm or wing-like forms, the plan was immediately discarded.

Once again, it holds true that(Heavy breathing) tactics based on the normal understanding of the common senses(Heavy breathing) are not always useful against these monsters. It wasn’t all for nothing, however.

In the process of analyzing this foe, we were able to identify a dark entity of humanoid figure within its body(Heavy breathing). While its exact functions are yet to be identified, our current assumption leads us to believe that it may be the entity’s main form, or its core.

I presume that its means of aggression will primarily prioritize attacks of physical nature using its bone structures, but… on account of the lack of evidence, I cannot say for certain.

Any missing information will be(Heavy breathing) supplemented by subsequent observations; please consult this guide in your(Heavy breathing) future commands.

Thank you.

→ Damn… by the book as always. How'd you even bring your whole template to a voice recording? (Rodion)

→ Easily. It is a skill to be expected from those in service of the Executive Manager. (Outis)

→ Yeah, I bet… Take some time to breath though, huh? There was a distracting amount of ‘Heavy breathing’ in this report. (Rodion)

→ Hmph. Must be the nervous breathing of inexperienced chicks. I, Outis, do not let such simple reports take my breath away. (Outis)

→ I-it wasn’t me. It’s been coming from that skull the moment we found it… (Sinclair)

→ Hmm. It has not the lungs nor the trachea, yet it breathes. Through where does its air travel, one wonders—how utterly bizarre. (Yi Sang)

We engaged with the entity in a meaningful capacity around 1100 hours today.

Its first actions in battle were to attempt to strike us physically using its bones. Just as we had expected.

Its most prominent form of attack involved extending its spine to maul its foes with its sizable jaws. However, another, unexpected form of attack was also observed.

It intermittently lets out a breath. The exhale carried an extraordinary level of shock and air pressure that dealt rather significant damage to any Sinners who were caught directly in its blast radius.

Our allies are far from the most reliable martial force, but a numerical disadvantage may easily lead to fatal results; please do take this advice into account.

However… it does not seem that this entity requires a high level of strategizing to defeat. Maintaining high pressure should be more than enough.

Another thing to keep in mind: after some time, it released a large volume of ‘air’ by exhaling.

The ‘air’ seemed to improve the poise of whomever breathed it in, enhancing the keenness of their attacks. This is when the shadow entity within the skull began to mobilize, attempting to steal the ‘air’ from all those who had it.

Various strategies were attempted to stop this process, but they were to no avail.

The most optimal, and the only strategy against losing this air would be to ensure that every unit individually resist the entity to the best of their abilities.

The entity’s attacks became highly augmented once it inhaled a large volume of this air; preventing this outcome must be the primary objective of this battle.

Concluding the report.

Thank you.

→ Recognition of 'Heavy breathing' was disabled in this report for the sake of legibility. However, the ‘Heavy breathing’ records of the previous report will not be removed in service of enhancing the sense of realism of the earlier report. (Faust)

→ Oh, yeah. The shadowy humanoid dragged Gregor in earlier… are you okay? (Sinclair)

→ … It’s not a good time, fellas. I thought the thing was tearing me apart limb from limb. (Gregor)

I write to inform you that further intel has been gathered during our encounter with the entity.

It was learned that, upon losing its ribs, the entity begins to prepare a highly fatal attack.

However, with the elimination of its protective skeleton, its defenses become highly porous, meaning that it became much more susceptible to our assaults.

On the other hand, while not destroying the ribs would inevitably lead to a prolonged battle, it would save us the trouble of having to come up with countermeasures against highly dangerous attacks.

Mm. This moment calls for a strategic judgment call.

I have faith in the Executive Manager that, as they have always done, they would come up with an excellent decision that takes the entity’s behaviors and other battlefield factors into account.

Thus, I leave this part of the battle to the Executive Manager’s brilliant strategic mind.

Concluding the report.

Thank you.

→ Cool… thanks. (Dante)

→ Is it just me, or does Dante seem a lot less… enthusiastic when replying to Outis? (Rodion)

→ No, no… that’s not what’s happening here! I’m very enthusiastic. (Dante)

→ Your alienation tactics will fail to drive even the smallest wedge between the Executive Manager and myself. Your efforts are for naught. (Outis)

→ No… I don’t think that’s what she’s trying to do either. Anyways, I want you to know that I really do appreciate these detailed reports… (Dante)

Mirror Dungeon Event

Mirror Dungeon Event

---

Shhhh-chk.

Shhhh-chk.

There is a skeleton, making ominous, labored noises.

There is a shadow of somebody in its spine.

Does the shadow breathe, one must ponder.

Pick up a respirator and put it in its mouth. Pride & Gloom Advantage check. Pass to gain a Poise E.G.O Gift Who will step forth? Pride / Gloom Advantage: ≥ 13 No Advantage: ≥ 26 Check Passed A single breath was more than enough. For the first time in their existence, they could breathe in and out as much air as they wanted without hurting. Every living second of their life was pain. No one will ever understand that. E.G.O Gift Nebulizer obtained! Check Failed Blowing air into its mouth was to no avail. There was a coughing noise not long after. Perhaps liberation is nigh. Nothing Happened.

Watch. The shadow in the skull was nothing but a lingering feeling. Resentment. Penance. All of it, to no avail. So it fades away in silence. All that remains is a hollow skull All Allies healed for 10 HP and SP. All Allies with the Pride Sin Affinity Attack Skill healed for 15 HP and SP.

E.G.O Gifts

Mirror Dungeon Encounter:

Tier: II Cost: 218 Poise PoiseBoost critical hit chance by X*5% for the next Y hit(s).

Nebulizer First Turn Start of an Encounter: all allies gain 4 Poise PoiseBoost critical hit chance by X*5% for the next Y hit(s). Potency and +4 Poise PoiseBoost critical hit chance by X*5% for the next Y hit(s). Count. When activating Pride Absolute Resonance, all allies gain 2 Poise PoiseBoost critical hit chance by X*5% for the next Y hit(s). Potency and +2 Poise PoiseBoost critical hit chance by X*5% for the next Y hit(s). Count at Combat Start. - [Cannot Stack] When Thoracalgia Ryōshū E.G.O Passive 「Breath」 activates, this effect does not activate

E.G.O

The Thoracalgia E.G.O is extracted from Sleeping Bag of a Bygone Day.

Both Ryōshū and Faust's E.G.O were added during Season 5, available through Extraction, with Ryōshū's E.G.O added as part of the LCB Regular Check-up Event. Both E.G.O are obtainable through the Dispenser and the Sinners' Target Extractions from Season 7 onward.

Thoracalgia E.G.O	Ryōshū Faust

Gallery

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  Idle Sprite
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  All parts broken
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  Idle Animation
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  All parts broken Animation
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  Evade
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  Guard
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  Hurt
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  Suppressed Core
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  Depicted in Ryōshū's Thoracalgia
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  Depicted in Faust's Thoracalgia
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  Battle Background

Trivia

• The name of this Abnormality's E.G.O, Thoracalgia, is a medical term referring to chest pains.
• The patch notes for the January 23rd, 2025 update referred to this Abnormality as Sleeping Bag of the Olden Days.

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