The Magical seed or Seed is an item that can be made using the Cauldron.
Magical seeds can be used during quests. Upon using one, a candy tree will grow in front of the character. Sometimes, a very rare yggdrasill tree will grow. According to the game's code, there is a one in one hundred chance that a yggdrasill tree will appear.
Making a Magical seed
To make a Seed, boil water (with nothing in the Cauldron) until it says either "Boiling... BOILING !" or "Boiling... the water is burnt ! How is that even possible ?" (either works), add 650 candies and click "stop" (there isn't a required amount of time the candy has to be in). Then bottle it.
Using 19500 candies you can make at once 14 cloning potions and 30 seeds. (As long as you make sure to fulfill the cloning potion requirement of getting to "Boiling... the water is burnt ! How is that even possible ?", Otherwise you'll just get the seeds.)