Manaland

From The Five Pillars

Mananodes are mountains, swamps, glaciers, deserts and forests which are all used to generate mana of the corresponding colour.

Mananodes can be created by casting the correct spells while you have free land.

Mountain give wild (red) mana and are gained by casting the spell Raise Mountain.
Swamp give old (black) mana and are gained by casting the spell Flood Land.
Glacier give elemental (blue) mana and are gained by casting the spell Call Winter.
Desert give plain (white) mana and are gained by casting the spell Clear Vegetation.
Forest give natural (green) mana and are gained by casting the spell Call Nature.

The more manaland of a certain type you have, the bigger your mana income per turn will be for that type of mana.