The Zephtelos Fortress (ゼフテロス砦, Zefuterosu Toride) is a location in Genso Suikoden Tsumugareshi Hyakunen no Toki.
Located in the southern reaches of the Holy Empire of Ionia, within the Apiro Desert, Zephtelos Fortress played a vital role in the HIY 100 Teras Pharma conflict. The fortress was staffed with some of the Ionian Army's elite, led by Empress Astrid herself.
Even after the conflict, Astrid's forces remained for some time. As such, the fortress would become the site for Astrid's investigations into the Yggdrasilian Throne following her meeting with the hero.
Over time, the importance of the fortress declined, and it fell into disrepair. Shortly after the HIY 200 Teras Pharma conflict a sand whale would crash into the fortress, dying, and completely destroying the fortress' remnants. By HIY 300, the area was known as the Behemoth Grave with Zephtelos Fortress a long-forgotten memory.
- Genso Suikoden Tsumugareshi Hyakunen no Toki The Complete Guide (ISBN 978-4-04-886462-6), page 92