Conjure Bog

Standing in front of your amphora, you submerge the freshly harvested troll heard, and begin chanting the words to the spell, commanding the water within to rise and spread around you. Over the duration of the spell, the terrain and land around you is magically transformed into a bog, or swamp, full of shallow lakes and streams of water. This can somewhat flatten hills or valleys, carve new valleys, and grow trees, shrubs, and other common swamp flora. The spell also fills your new bog with swamp creatures, for example, frogs, snakes, crocodiles, or trolls which are summoned during the casting (starting with the lowest CR creatures and increasing over the duration). This spell can conjure any number of creatures with a combined challenge rating not exceeding your wisdom modifier multiplied by the level at which this spell is cast. The spell also damages any structures or dwellings in the area, as if they had been within the swamp for 100 or more. a wooden structure might erode due to rot, and a stone structure might become covered in moss and other vines.

The swamp is approximately circular around the caster, and slowly extends around the caster during the casting to a maximum diameter of 1 mile once the spell is complete. 

If the spell is successfully cast, the effect is permanent. if the casting is interrupted, any damage to structures remains, but any summoned creatures are unsummoned, and any terraforming to the land is reversed.