Scions of Tomfoolery
A note about realms
There are thirteen realms that orbit Eberron like moons. As these moons orbit closer or farther away they may affect the planet, or they may not, depending on the magic associated with the moon. These moons are common knowledge, although their effects (particularly the effects of the moons most likely to cause huge shifts in Eberron civilization) are not necessarily something that the average individual thinks about all that much. No one is particularly worried about the daelkyr returning, for example.
When the daelkyr from Xoriat, the Realm of Madness, invaded it was because Xoriat was orbiting close to Eberron, making the magical barrier between the two porous and thin.
The Gatekeepers stopped the invasion because they found a way to move Xoriat farther away from Eberron, and then banished to Khyber the daelkyr now trapped and unable to return to Xoriat.