Admittedly, my definition of such things might be colored by how magic operated on my star. Though, truthfully, this seems to have an intelligence behind it.
You are correct in your assumptions. Initially, there is a dark marking upon one's hand. One might find some discomfort or pain there after some time, but it does not appear to be an injury for it does not heal. The nightmare itself takes the dreamer to the darkest, deepest parts of the ocean.
So vivid is the nightmare that one might find themselves out of breath as though they were the one drowning.
private;
You are correct in your assumptions. Initially, there is a dark marking upon one's hand. One might find some discomfort or pain there after some time, but it does not appear to be an injury for it does not heal. The nightmare itself takes the dreamer to the darkest, deepest parts of the ocean.
So vivid is the nightmare that one might find themselves out of breath as though they were the one drowning.