Wisps are a non-entity, flame-like mob. They spawn near trees and can be caught with Jars. Catching them is not easy, as they will flee when a player is too close and can phase through solid blocks when chased.
After being caught with a Jar, the Jar can be placed and will provide benefits to the environment around them.
Red Wisps in Jars will destroy all plants in a 10x10x10 area, making them useful for keeping weeds away, but also dangerous to gardens.
Green Wisps in Jars will accelerate growth of plants in a 10x10x10 area, there is no constant rate, so it may take the plants no longer than usual to grow, or they could fully grow within seconds.
Blue Wisps in Jars will prevent fires in a 10x10x10 area, making them useful for protecting flammable builds.
If you want to spawn a wisp, use the /add_wisp command. You can specifiy a color(red, green, or blue), but if you don't a random color will be picked.
If you want to clear all wisps (excluding those in Jars), use the /clear_wisps command.
This mod is W.I.P, and will be taking the back burner as other projects are more important.