A DC of mine, a shadowy, suspicious guy wearing a hooded sweatshirt, entered my dream last night and overpowered both my DG and myself, causing me to wake up and blocking me from any further contact with the dream world all night. Even WBTB yielded nothing. How could this happen?
The DC reminds me a lot of the Jungian shadow, I agree with Li10 in saying the DC is a personification of anxiety, stress, or something. The DC definitely earns its name (Nemesis).
If you enter a conscious state you might want to ask what Nemesis wants or something. Things like this always seem to pass in time.