A realm is a great sphere of existence within the Veil, each containing many worlds. Although separated by the Veil, they are all surrounded by the same Dream, Ether, and Void. Souls that pass on to rebirth may be reborn in a different realm than where they originated, provided there are sufficiently similar children to become.
Teleportation magic can allow access to different realms, via ritual circles with defining symbols and numerological keys. There are six realms commonly known to the Elkandu. The seventh realm, accessible by the numerological key of 9, is the Temporal Realm, passage through which allows time travel. No one is entirely certain of its existence beyond the mere speculative and theoretical.
Nothing is known about the Chimerical Realm aside from it being the origin of those with chimerical souls – that is, shifters. Nothing at all is known about any realms beyond eleven, aside from speculation.