In phase 2, one holding can be played, regardless of whether a realm was played, rebuilt, or not played at all. Although it does not need to be attached to the same realm just played or rebuilt, a holding must be attached to the realm of the same world. (Logos on the cards must match).
Some holdings can be placed with any realm, for example, Blood Moon (107/Prime). This kind of power is stated in the card's special powers. Some holdings have unique powers activated upon an attack against the attached realm. However, others have special abilities that are always in effect.
Each realm can only have one holding. It is impossible to move a holding to another realm or remove it voluntarily unless another card's special power removes it. Upon razing the realm, all Cards attached to it are discarded unless the card's special power instructs otherwise. It is impossible to attack a holding and the attached realm separately.