Attacks in Dreaming

From Mia: Attacks in Dreaming

A document on the site contains certain warnings. Among them is one that so astounded me: "exit dreams whenever you feel that someone (a dream character) forcibly inserts some vile substance into your upper palate through your mouth. (If you have experienced such dreams, you should engage in 'mental' cleansing, tracking the imprinted program within you that 'impedes' your development. Its effect may manifest as drowsiness, loss of interest in previously captivating subjects, etc.)"

For literally the past year (this never happened before, and I've been having Lucid Dreams for a very long time) exactly these things have started happening to me. I must say right away that it is sickeningly repulsive. I try to fight them every time (I don't know who they are, but they are clearly not friendly), and when my strength is exhausted – I wake up.

Please enlighten me: what and who are these entities, why specifically the upper palate (is that where the dreaming's attention is concentrated?) and what should I do.