Dream-alters or dream-members are like walk-ins and soulbonds, that come directly from a dream.
They come directly from a dream, as if following the dreamer out of their dream and into the collective mind as a member of the system.
They can either have their memories intact if they are sourced, or come in without memories or source. Their source could be from the dream or they could have a source of someone or something in shared reality. They may also just appear as someone or something in shared reality and not be sourced, since dreams sometimes use things the brain already knows to fill in needed roles for the story of the dream. Dream-members may have their own identities and their own personal lives that have nothing to do with their source or faceclaim.
Usually, dream headmates may all come through together and may all possess the ability for dream seeking, this may or may not be true for all who come through.