By offering several items to the Goddess Gaia, you can carve your will into the world and change the climate of a defined area. By placing in items into the eight Arcane Plinths, and defining an area with bloodstone bricks (of either type), you can change the biome of the defined area to a biome that is within a given set of specifications.
A defined area means any area that is contained within the Blood stone, and has a definable path to the Master Ritual Stone. Basically, if you place water on top of the Master Ritual Stone, and continue to place water where the water flows until you can't place any more, that will be the area that changes. The definable area can only be defined one block above the Master Ritual Stone, and the max range is a 21x21 area.
The ritual assumes first of all that you have a humidity of 0.5 and a temperature of 0.5. It will then consume the items that you have placed and modify the humidity and temperature accordingly. It also starts with assuming that a range of 0.1 is acceptable in both directions. If the ritual can not find a biome that is registered in the list, it will simply set the biome to a "plains" biome, with a biome ID of 1.
The items that can modify these parameters are as follows:
Sand: humidity - 0.1
Sandstone: humidity - 0.2
Netherrack: humidity - 0.4
Lapis: humidity + 0.1
Water bucket: humidity + 0.2
Lapis block: humidity + 0.4
Coal: temperature + 0.1
Coal block: temperature + 0.2
Lava bucket: temperature + 0.4
Snow ball: temperature - 0.1
Snow block: temperature - 0.2
Ice block: temperature - 0.4
For this to take effect on the client, you will need to relog. This will be fixed in the future if possible.
Oh, by the way: this ritual requires 1,000,000 LP per activation. Have fun!