Sinistea cannot hold its shape without a container. It spills like a liquid from the center of wherever it is placed. If its cup breaks, Sinistea will reform in the nearest available cup-like object.

Polteageist that grow too big for its teapot (physically or emotionally) will search for a bigger home. In fall, you may see many Polteageist line up by a discarded piece of china. When a Polteageist of the right size enters the new pot, they all scramble to swap their old ones.