The Ionite Nebula was a nebula located near Luria. Few Lurians traveled far from it.
In 2372, Drex, son of Martok, asked Morn why he was so far away from the nebula. (DS9: "The Way of the Warrior")
This nebula was only mentioned in dialogue.
Drex's line about the Ionite Nebula was not mentioned in the script of the episode and may have been added later.