What novel by James H. Schmitz involves a type of theoretical or fictional entity existing in a dimension beyond our own?
The Witches of Karres:  It deals with a young space ship captain who finds himself increasingly embroiled in wild adventures involving interdimensional alien invaders, space pirates, and magic power. Interdimensional being: An extradimensional being or intelligence (also intra-dimensional and other-dimensional) is a type of theoretical or fictional entity existing in a dimension beyond our own.
i don't know