Istreus is the god of secrets in the Empyrean Cult, lord of knowledge gained through effort and discipline; what is taken by shortcut — sacrifice, pacts with what lies below — is outside his domain.
| Type | Deity |
| Spheres | Knowledge, learning, magic |
| Symbols | Silver crescent; tower |
| Sacred animals | Owl, ibis |
| Spanish entry | Istreus — Maestro de Secretos, Vidente sin Ojos |
The Tower of Knowledge
The Tower of Knowledge, in Medieval Vala, is consecrated to him. There enchanted items are appraised and identified — its sage recognized the power of an enchanted knife put up for sale — a treasurer works, and scholars are trained. A mage from the tower travels up the Blackwater with the fortune-seekers of the frontier in 724.
Frontier sources distort his name as “Estregos”.