The first step is to list your associations. It's best to pick individual items and list everything that comes to mind without worrying at first what the overall interpretation is going to be.

So for instance, list your associations to Seth. What do feel about him? What is relationship to him? What do you associate with him talking to someone? Then do an empty, dark dining room and living room. (The invisible person, and a 'living room' with no people in it, sounds like an absence of people where they are supposed to be living.)

List your associations to Blank. Do you have any idea why he wants to kill you? Do you associate to any person in your life?

Getting killed could represent a loss of your psychological life, so this Blank could be a part of yourself who wants to come forward and express himself, yet you fear if that happens a loss of the qualities of your life that you most associate with being alive. Blank is not necessarily a bad part of yourself. Blank could have qualities that are valuable to your life, yet you fear those coming forward.

A classroom full of people contrasts with the empty dining room. There are now people where you expect people.

What do you associate with an African theme? With Africa?

What do you associate with a male teacher? Are you still in school by the way? If so, you could associate him with being an authority figure. Or maybe you like him a lot.

Maybe Blank is your anger. I get that association from "seeing red."

The class goes on like nothing happened. Maybe the dream is saying that if you let your anger out, nothing bad will happen. Perhaps you need to integrate your anger with your conscious personality.

EDIT: it seems to be typical of dreams that occur throughout the night that the earlier dreams lay out a problem, and the later dreams have more of a possible solution to the problem or a suggestion of what could be different for the better.

Mike