Syntax: advance, advance [stat]
Once your character has earned enough experience, you can advance your level. This must take place either in the adventurers guild, or some other area that allows this. (Most guilds have a room for advancement).
On the mortal levels (1-19) you can advance stats above your own level to a certain point, but once you've become an eternal player you can only advance them to match your current level. Advancing stats is much like advancing your level; you need to be in the Adventurers Guild or some other room that allows this.