"With that, she (Vaermina) pulled the void away, and for hours each night she would reveal to Darius the most horrible perversions of nature. Men being skinned and eaten alive by other men, unimaginable beasts of many limbs and mouths, entire populations being burned -- their screams filled his every evening."
―Unknown in Sixteen Accords of Madness, Book IX.
Vaermina is - as you a Telvanni know - a daedric prince, closer: the Prince of Nightmare. Her realm of Oblivion is named 'Quagmire' and described as permamently changing nightmare. Since of lately Heimlyn Keep has been suffering from bad dreams influenced by even this daedric prince.
Vaermina has a strong interest in psychological terror, so that is what you, pityful creature, have to expect. Your dreams will be haunted by your deepest fears, your most painful memories and the most horrible pictures your mind can imagine. But not just that! You thought it could be bearable? It won't be just one Fear, one Memory for the night: there will be many following you, shifting scenes one more horrifying than the last one. And they seem so real that you are not sure if you even woke up yet.
Her sphere of influence includes nightmares, psychological terror and torment, dreams, bringing evil omens, and stealing memories.
.. you remember. Omens. What, if after all, those are no dreams?