School transmutation; Level cleric 7, druid 6, sorcerer/wizard 7, witch 7
Casting Time 1 hour
Components V, S, M (10,000 gp worth of precious minerals, see text)
Range 100 feet
Area 100-foot-radius emanation, centered on you
Duration 1 day/level (see text)
Saving Throw none; Spell Resistance no
You alter the area's terrain and climate to a new terrain and climate type appropriate to the planet or plane. For example, you might transform a desert to plains. To cast this spell, you must expend 10 uses of mythic power along with the material cost. This magically alters the area's climate and normal plants to those appropriate to the new terrain, but doesn't affect creatures or the configuration of the earth. Transforming rocky hills into forested areas converts grasses into shrubs and small trees, but doesn't flatten the hills or change the animals to suit the new environment.
You can alter the climate by one step (warm, temperate, or cold). The maximum extent of the terrain change is up to the GM, but in general is to a similar terrain type or one step within that terrain type (such as from a typical forest to a forest with massive trees or light undergrowth, from a shallow bog to a deep bog, and so on). You might be able to shift the land to a similar terrain type, such as turning a sparse forest into a relatively dry swamp. Local creatures adversely affected by these alterations either flee the area or quickly die, depending on their mobility and awareness of the change.
Multiple castings of the spell in the same area can create an area with radically different terrain and climate than the surrounding land. The GM can decide that certain terrain shifts are unsustainable and shorten the duration, or that some are suitable for the area and extend the duration.
This spell could have many secondary effects based on the nature of the change, the type of bordering terrain, and so on; these should be determined by the GM on a case-by-case basis. For example, transforming a desert requires drawing water up from underground to sustain the plants, which could deplete the water table in nearby areas. Creating a warm desert in the middle of a snowy tundra will create a bordering area of mud and frequent storms from the clash of hot and cold air fronts.
If you're at least 8th tier, you can expend 20 uses of mythic power instead of 10 to increase the range to 1 mile, the area to a 1-mile-radius emanation centered on you, and the duration to 1 month per caster level.