Glad it was helpful. If you feel up to it, want to add a glossary somewhere on the wiki? That would probably help newcomers keep things straight.
Wakened marines, perferably ones who have just woken who are unlikely to fall asleep again any time soon. They stand guard over their sleeper and dreamer brothers. Think of them as an honour guard for everyone currently in a coma for whatever reason. Some watchers hide amongst the sleepers and pretend to be asleep themselves while others guard doors and so on. Any marine, pretty much regardless of rank, may be called upon to perform the duties of a watcher at one time or another.
- Dreamwalkers These are the dreamers who are astrally projecting themselves into the warp. The August Dreamwalkers in Iron are the librarian dreadnoughts that act as dream guides when exploring the warp, even moreso than normal librarians do. They spend whole centuries asleep and roaming the warp with their minds before being woken again and called to battle once more.
>(also, if I understood correctly, lucid dreams are some sort of visions of the future, correct ?)
The exact opposite actually. Lucid dreams are simply dreams you can control. The visions of the future, the prophecies that the dreamers sometimes get, are almost entirely OUT of the dreamer's control and basically just get forced into their mind for them to experience whether they want to or not.
Since there are Apothecary Dreadnoughts for the Sleepless, do they still require the attention of regular Apothecaries, or not at all ?
The Sleepless are administered to by the entire apothecarion. In battle, and pretty much any other time that the Sleepless are being given weapons there are always Apothecary dreadnoughts around to subdue them quickly should they try to kill their brothers.
You can never ask too many questions.