In Eberron, all aberrations share a common bond. Thousands of years ago, beings known as the daelkyr led an extraplanar incursion into Eberron. True lords of madness, these shapers of flesh brought with them a host of horrors from the plane of Xoriat. As the daelkyr sank their talons into Eberron, they twisted and corrupted any other creatures unfortunate enough to fall into their clutches. Eventually, the shapers of flesh were defeated and sealed in the underworld of Khyber, where they continue to create new terrors even now.
But the daelkyr were not responsible for all of Eberron’s aberrations. According to myth, the world was formed from three dragons. Eberron, the Dragon Between, is the source of all natural creatures, and Khyber, the Dragon Below, spawns fiends and aberrations. So while the daelkyr create monsters in the darkness of the underworld, Khyber continues to generate horrors of its own.
Although many aberrations -including beholders, mind flayers, and grell – are natives of Xoriat brought to Eberron by the daelkyr, their creature type remains aberration, not outsider. Just as elementals and lycanthropes can be found on Lamannia and fey exist in Thelanis, aberrations have a place in Xoriat.
Except for matters relating to history, the material in Lords of Madness dovetails quite nicely with that in the Eberron books. For example, aboleth tactics, glyphs, and feats can be taken directly from the book, but a DM wishing to use these creatures must decide how they fit into the history of Eberron, Khyber, and Xoriat. The following sections look at each of the chapters in Lords of Madness and suggest ways to adapt the featured aberrations for use in an Eberron campaign.