Encroachment is one of the most severe anomalous consequences in the world of YiHuan. When anomalies are not addressed promptly and continue to spread, the surrounding real space is gradually eroded and rewritten by anomalous energy — a process known as Encroachment. Once Encroachment occurs, the eroded areas undergo permanent changes that cannot be restored.
Specific manifestations of Encroachment include local alterations to physical laws (such as disordered gravity directions, changes in matter permeability), distortion of spatial structures (such as passages and rooms that don't exist in normal space), and abnormal time flow. Encroached areas typically continue to produce Oddities and attract more anomalies, creating a vicious cycle.
Certain areas around Hethereau have already been affected by Encroachment, and these areas are marked as restricted zones by the Bureau. Parts of Groth Island show signs of Encroachment. The primary mission of Espers is to eliminate anomalies before Encroachment occurs, preventing more areas from suffering irreversible erosion. The Circle organization appears to be intentionally creating Encroachment phenomena, with purposes related to ancient prophecies.