The Alice Game is the "game" or battle that all of the Rozen Maiden must participate in to meet Rozen, their Father.
The Alice Game is Rozen's plan to find the doll who is worthy enough to become "the perfect girl", Alice. It is said that whoever becomes Alice is loved most by Father and will be able to personally meet him.
It is seemingly won by fighting and collecting all of the Rosa Mystica, but this is later proven incorrect. If a doll's Rosa Mystica is not willingly given to another doll, the Rosa Mystica will hurt the recipient doll. It is discovered that the way to win the Alice Game is by forming strong bonds with the other dolls.
By winning the Alice Game, the winning doll will be granted a wish by Rozen.
In this adaption, taking another doll's Rosa Mystica will not hurt the recipient doll. This is the only adaption where taking another doll's Rosa Mystica will grant the abilities of that doll.
Alice is known as the "perfect girl" in the Rozen Maiden series; she is also the winner of the Alice Game. Whoever becomes 'Alice' in the Alice Game gets to meet Rozen, or "Father", as the Rozen Maidens call him. As described by Shinku, Alice is "more pure than any gem, more noble than any flower, unspoiled and flawless." She has also been considered to only exist within Rozen's mind. Rozen's attempts at creating Alice resulted in him creating the Rozen Maiden Dolls, but all of the attempts failed, and that led to the Alice Game.
Alice is shown in the anime, in one episode and in the introductory clip of the first season, and the same view of her is given in the manga; she is only shown as a silhouette of a beautiful doll. She bears a resemblance to Suigintou, or rather, Suigintou bears a resemblance to her, since Alice appears to have wings.
There are a few Rozen Maidens that do not want to be Alice because it would mean taking away other dolls' Rosa Mystica by defeating them in battle. These dolls are Shinku and Suiseiseki.
At the end of the series, Shinku ends up becoming Alice after Kirakishou is unable to absorb the rest of the other Rosa Mystica. She appears to become human, at least briefly while she talks to Rozen, and her hair becomes incredibly long.
Masters are humans who have become contracted to a doll. In order to keep a sustained presence in the real world, the human masters provide a form of energy to the doll.
In older media, this title was "medium".
Rosa Mystica are the artificial life forces that the Rozen Maidens possess. They are in the form of small sparkling gems, each surrounded by several glowing orbitals, similar to the structure of an atom.
They were created by Rozen and are pieces of his own soul. They used to be a singular form, but were separated apart as Rozen created more and more dolls.
Once a Rozen Maiden loses her Rosa Mystica, it is absorbed into the body of the maiden who has defeated her. A Rozen Maiden turns into a regular doll after having lost her Rosa Mystica.
In Rozen Maiden (Anime)
A doll who absorbs a Rosa Mystica will also gain the abilities and powers of that doll.
It is shown that the Rosa Mystica can choose it's allegiance, as Souseiseki's Rosa Mystica went to Barasuishou to join Suiseiseki's, when Suigintou was defeated, while Suigintou's went to Shinku. If anything other than the original seven Rozen Maidens that attempts to absorb the Rosa Mystica they will not be able to contain it, and will be destroyed, as shown by the fate of Barasuishou.