See the Basic Editing page for markup rules. It is recommended that you use an existing page as a template. To do so, simply open an existing page and click the Edit link on the righthand toolbar, then copy the contents to your new page.
Generally, the style is expected to follow a pseudo-encyclopedic/academic/historical format.
Any character can have their own page, so long as there is enough information to merit it. For minor characters, it is probably better to list them as a subsection under a related page. For example, Lakhnatha could have a Notable Residents section that lists minor characters by name, along with a short blurb.
Remember that a character's page should focus on a factual and dispassionate account of their history. The wiki is not a place to advocate for your favorite character, so you should generally avoid phrasing events in a way that attempts to justify a character's actions or applies value judgements. A wiki page should simply provide an objective description. If you want to provide insight into motivations or feelings, that can be done in its own section (e.g. Psychology, Beliefs, etc.).