The Crest Stone of Seiros is a Crest Stone that debuts in Fire Emblem: Three Houses.
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The Crest Stone of Seiros is the main method of attack used by the Immaculate One during the endings of the Crimson Flower and Silver Snow routes: The Fight for Fhirdiad and The Final Battle, respectively.
Upon entering its second phase during the latter chapter, the Crest Stone of Seiros upgrades to the Real Serios Crest Stone, increasing its effectiveness.
|Inventory (Unobtainable)||Chapter 21 (Silver Snow) - The Immaculate One (first phase)|
Chapter 18 (Crimson Flower) - The Immaculate One
|Inventory (Unobtainable)||Chapter 21 (Silver Snow) - The Immaculate One (second phase)|
- Zooming in on the Immaculate One's battle model will show the Crest Stone of Seiros in its forehead, with the text "The High Priestess" and "II" engraved on it.