Delusion

Biodata

Power Progression

Appearance

• Teppei’s Electro Delusion: A purple glass orb, initially dull. After Wu Yi supplies it with vitality, it shines intensely and releases violet lightning 2.
• Wu Yi’s set: Seven faintly glowing Delusions strung together as a long ornament at his belt, normally concealed beneath his clothing 5.
• Rosalyne’s Cryo Delusion: Found shattered among her ashes after the Raiden Shogun kills her at Tenshukaku 8 9.

Abilities & Limitations

Elemental Power Conversion

A Delusion absorbs vitality and converts it into elemental energy 2.

• Grants substantial fighting strength even to an ordinary person without combat experience 4.
• Its output can be increased by supplying vitality directly, as Wu Yi demonstrates with the Power of Abundance 2.
• Resistance-issued prototypes are substantially inferior to the specially made Delusions carried by Harbingers 5.
• Rosalyne considers the possibility of Wu Yi independently producing every elemental reaction with his seven-element set, but this remains her speculation 5.

Vitality Consumption

Unmodified Delusions place a potentially fatal burden on their users 2 7.

• Teppei: Repeated use whitens his hair and exhausts his vitality completely, causing his death before Wu Yi revives him 2.
• Resistance soldiers: Multiple users suffer damaged vitality and require treatment 2.
• Kolya: Prolonged use leaves hidden ailments severe enough that a Snezhnayan doctor gives him no more than three years to live. Wu Yi later cures these conditions 17.

Stored Life Force

Wu Yi’s modification substitutes a preloaded supply of vitality for the user’s own life force 4.

• Allows use without the ordinary life-draining side effects while the stored supply lasts 4.
• The reserve is finite, though Lumine’s gift is described as holding enough vitality for her to defeat Childe roughly a thousand times 4.
• Wu Yi states that he can withdraw his power from Delusions made with his assistance if the Fatui violate his conditions 7.

Flame Suppression

A Cryo Delusion can also restrain Rosalyne’s destructive flames 5.

• Pierro gives Rosalyne one when her power as the Crimson Witch of Flames is close to consuming her.
• It temporarily seals those flames, enabling her survival and subsequent recruitment into the Fatui 5.

History

Fatui Development

Delusion production makes extensive use of technology from ancient Khaenri'ah. Rosalyne describes Delusions as early-stage prototypes for a broader weapons-development program, with their enormous side effects forming one of its major bottlenecks 7.

The Fatui also produce specialized versions for their Harbingers. Rosalyne receives a Cryo Delusion from Pierro after becoming the Crimson Witch of Flames, centuries before Wu Yi’s arrival in Teyvat 5.

Distribution in Inazuma

The Fatui secretly supply Delusions to Resistance soldiers while concealing their side effects. Teppei mistakes his for something comparable to a Vision and repeatedly uses it in battle, ultimately exhausting his life. After Wu Yi revives him, Teppei renounces the device and hands it over 2.

Kokomi permits Wu Yi to keep Teppei’s Delusion and gathers other affected soldiers for treatment. The Resistance subsequently confiscates its Delusions, reducing its combat strength before a major Shogunate attack 2 4.

Wu Yi’s Research and the Factory Raid

After studying Teppei’s Delusion overnight, Wu Yi adds a life-force reservoir and gives the modified device to Lumine before her raid on the Delusion factory. Using it alongside her three elemental powers, she fights Scaramouche to a standstill. Scaramouche retreats, and Lumine and Yae Miko destroy the factory 4.

Wu Yi obtains additional Delusions from Kokomi and continues modifying them between medical duties. Reports of his work attract Rosalyne, whose initial willingness to seize his technology by force disappears after she sees his charged seven-element set 4 5 6.

Recruitment Agreement

Rosalyne offers Wu Yi access to advanced Delusion research and custom-made Harbinger Delusions of all seven elements. In return, the Fatui want him to treat soldiers suffering side effects during weapons development. She also assures him that he may retain the rights to his technology without sharing it 7.

Wu Yi’s conditions specifically restrict future Delusion use:

• No foreign test subjects: The Fatui must stop testing Delusions on people from other nations 7.
• No overseas factories: Every Fatui Delusion factory outside Snezhnaya must be destroyed 7.
• No foreign warfare using his work: Delusions made with his help must not be used in wars or conflicts against other nations 7.

The Tsaritsa accepts his conditions. The provided account confirms her agreement, but does not document the dismantling of every overseas factory 8.

Notable Users & Custodians

• Teppei — Original holder of the Electro Delusion studied by Wu Yi; relinquishes it after being revived 2.
• Wu Yi — Researcher and modifier who supplies vitality through Abundance, develops the storage modification, and carries a charged seven-element set 2 4 5.
• Lumine — Receives Wu Yi’s modified Electro Delusion and uses it against Scaramouche 4.
• Rosalyne / La Signora — Carries a specialized Cryo Delusion that suppresses her flames; it is shattered during her death at Tenshukaku 5 8.
• Kolya — Fatui officer whose long-term Delusion-related ailments are cured by Wu Yi aboard the ship to Snezhnaya 17.