Mirage arcane

Mirage arcane, sometimes known as mirage arcana, was a powerful illusion spell that could alter most aspects of the appearance of a vast area.

Effects
For up to 10 days, the spell could make terrain in a region as large as a square one mile (1.6 km) on one side assume the form of any other terrain. The illusion affected all sensory appearances: visual, audible, tactile and olfactory. Even structures could be made to appear or be hidden by it. It could not, however, conceal creatures or create illusions of them.

The illusion could be detected via true seeing and creatures aware of it could see through it. However, it continued to physically manifest and interact with a creature aware of it.

Components
The spell required only verbal and somatic components.

History
The spell was attributed to Netherese arcanist Zahn in -927 DR and was originally known as Zahn's mirage.