A dream or vision about a pen, including the quill, ballpoint, fountain pen, etc. tells you about need for self-expression and communication, expressions and creative ideas that you can experience. Another explanation is that it will do you good if you put your feelings on paper.
Also a writer, artist, creative person or a book reader must learn to communicate creatively and socially which is important for your growth in life. The pen reflects your soul, your source, your base and everything associated with it. You are, as it were, the pen and that on which you write.
It is a connection with your deepest and purest self, this can represent the dark (inner demons) as well as the visible qualities or outer appearances (soul forms). Your soul, your source, your base, your heart, your intuition knows what it wants to express, share, make visible. Communication with yourself and with the world around you (including your spiritual world) and/or the world of the past, present or future.