Generally, dream interference is impossible or at least difficult within consecrated ground or a manifest zone.  :-)<br/><br/>(protection from evil also offers protection, although the manifest zone thing can be gotten around with specialized spells typically folded into the function of a Riedran Monolith, and protection from evil can be countered by neutral Quori... although those are really really rare.)<br/><br/><br/>Ye Olde Cosmic Evil comes in three main flavors in Eberron:<br/><br/>1. The Daelkyr (Chaotic Evil)  Insane immortal monsters from the plane of Xoriat, the Daelkyr are strong, but mostly dangerous for their massive cults and nearly endless swarm of aberration progeny.  Daelkyr are fairly well known, since they're the enemies of the Gatekeeper sect of druids, although their names and specific ecology can be somewhat obscure.<br/><br/>2. The Raksha (Neutral Evil) The Raksha are the heralds of all demonkind, and the most commonly encountered on the surface of Eberron.  Hence, their lords are known as the Raksha Rajahs, nearly divine beings of almost unimaginable power trapped within the depths of Khyber.  Fortunately, they were sealed away, but as demon populations increase and reach the surface, they might just be able to awaken and completely destroy Eberron.  The Silver Flame works to defeat the Rajahs, as do the dragons of Argonessen.<br/><br/>3. The Quori (Lawful Evil) The Quori are the lords of Dal Quor, the realms of sleep.  For many years they were benevolent guardians of dreams, but something caused them to want more power, and they invaded Eberron to get it.  The Giants chased them out of Eberron, and in their exile, the Quori became twisted and evil.  Knowledge of the Quori is extremely rare, because only the most senior Kalashtar know of them, and they will very, VERY rarely reveal their existance to a nonkalashtar.  (since the Kalashtar are Quori as well, and therefore part of the same cosmic evil they must fight.)