"Because their ability to influence the world directly is so weak, Aengudaemons work by proxy: they act through followers. They build cults or orders of followers with which to further their goals and thwart the goals of their enemies. While in truth they are not innately good or evil, daemons are seen as evil by the Descendant Races and thus have a tendency to align themselves with isolationists, outcasts, "evil" groups or any other group that is separate from or shunned by most of mortal civilisation as they are. Likewise, while generally trusted and viewed as innately good by most of civilisation, there are aenguls that coldly focus on achieving their goals at any cost. One of the most potent powers of any aengudaemon is form a magical connection to their followers, allowing them followers, to draw on its magical power. This grants the followers magical powers akin to an arcane mage which are not hampered by the impermenant nature of arcane magic. However, drawing on too much power too soon can overwhelm, physically harm or even kill a user of aengudaemonic magic. Thus, like an arcane mage, an aengudaemonic mage must learn to control their magic before growing more powerful. Forging the initial connection usually requires the help of the aengudaemon or more commonly powerful mages of the order or cult, and thus to gain an aengudaemon’s magic one must share the motives and goals of the aengudaemon and their followers. When manifest, an aengudaemon is akin to a powerful mage in magical power, even though it can only use a fraction of its true power and whenever it does it risks temporarily binding itself to the physical world. When unmanifested, an aengudaemon can channel its power through several followers, resulting in several powerful mages and no risk of harm to the aengudaemon itself. Aengudaemons work via proxy because it is both far more effective, far more efficient, and because the risk to the aengudaemon itself is practically none. Because of this, the colder and less empathic aengudaemons may view the world as little more than a game: the death of a pawn is a setback, not a tragedy. Once an aengudaemon has allowed a mortal mage to draw on their power, they can no longer stop them from doing so. If one of their followers goes renegade and continues to use the aengudaemon’s magic, the aengudaemon will send their loyal followers to hunt them down and use severing magics (usually known only to the highest mages of the order or cult) to cut the rogue off from the aengudaemon. The only other way to sever the connection is to remove the aengudaemon from the world, as was the case with Aeriel and Iblees at the end of the Undead War."
This was pulled from the Aengudaemon lore, and such is the reason why disconnection is a spell. Though I may be wrong about this still being a thing, and if so my bad on being wrong.