Here is the full list of all 18 Gods of Havoc: Fall to Earth achievements.
You've summoned an angel.
You've summoned a mega angel.
You've summoned a demon.
You've summoned a plague Demon.
You've called forth rabid lions.
You've called forth Warewolves.
You've called forth Warebears.
You've converted an enemy army.
You've exploded an enemy army.
You've healed an army.
You've knighted an army.
You've blessed a city.
You've created a disaster.
You've magiced up a fort for your people.
You've created a mana tree.
You've sought out henges.
You've set traps.
You've woven webs.