Terraforming Plus
The cleanse the lands spell is now an avatar spell.
Researching a new skill called Greater Terraforming will automatically grant you several variations on it as well to turn terrain into other terrain types.
Simply research Terraformer when it shows up in your spell book to gain access to Greater Terraforming.
Creation specialisation now has the Mass Heal spell instead of Cleanse the Lands. Mass Heal heals 50% HP of every unit in target stack on the strategic map.
Cleanse the Lands now costs 20 mana to cast.
This mod used to be included with Cosmic Happenings Expanded, but is now standalone for your playing pleasure.
Have fun!
Icon source: http://www.iconarchive.com/show/flat-jewels-icons-by-pixelkit/Weather-icon.html