Planes of Sturth

Sturth has no "planes" in the conventional sense. Rather, the magical anomalies leftover from whatever disaster caused the Exodus have torn asunder the barriers between time and space.
Now, the influence of other, largely horrific timelines has leaked through in places where the barriers are thin. These physical places often bear the scars of what alternate times are leaking through.
Much of what people consider "demons" on Sturth are the malevolent influences from these alternate realities. Additionally, certain anomalies are severe enough to affect the very weather, called Arcane Weather by locals.