(Hmmm… just noticed we don't really have a "game theory and design" folder, so here we go, since this isn't "code".)
I'm curious as to how you all define the goals of your game. I realise for many, this has never been questioned - it's a MUD, duh! I have a short blurb in my first room that sums it up:
Basically, it's a game about killing "mobs" (mobiles or monsters) for "xp" (experience points) and wearing the right "eq" (equipment) to boost your "stats" (see 'help score'). Gaining and practicing the right skills helps a lot, too.
But, beyond that, how does your game work? How does a player "win"? Can a newbie with the right EQ kill a boss mob? Can a naked Hero, if he has the right skills? Do you need both? Do you have any measure of advancement other than levels?
I describe my mud as "a fast and furious PK mud, designed to test player skill in terms of pre-battle preparation and on-the-spot reflexes, as well as the ability to adapt quickly to new situations." The goal is basically to fight and overcome a wide variety of different opponents. As with most muds you can't actually "win" the game, but there are many different challenges to win.
A newbie character with the right setup (of which equipment is only one part) and sufficient skill can defeat mobs much stronger than themselves. The hardest of the (optional) newbie tasks involves defeating an opponent twice your strength, but I've seen some players win against even tougher odds. Conversely, I've also seen players accidently killing themselves during combat, and one newbie even manage to lose a fight against an inanimate object…
Different character builds rely on equipment to varying degrees - some are unable to use any equipment at all, others are heavily dependant on weapons and armour, and others fall somewhere in between. Of course a character specifically built around equipment-enhancing powers will do badly if stripped of that equipment, but it's certainly possible to play very effectively without any equipment at all.
Characters have a 'Divine Age' which works a bit like a level, at least in terms of measuring advancement. Your Divine Age is calculated by adding together your eight stats, and your stats can be trained by spending Primal (i.e., experience points). Primal can also be spent on powers, with the maximum amount of powers depending on your Divine Age.
I'd describe the goals of The 7th Plane as 1) exploration, 2) knowledge and 3) acquisition.
To elaborate on these, in reverse order, the goal of acquisition relates to stat building, accumulating currency, power and material goods, all through various means, often requiring extensive knowledge of the skills available and the subtleties of the game mechanics. The goal of knowledge is to learn the system, knowing when to fight or flee, if certain resources are more valuable to you than others, whether an area is trapped or if there is a puzzle to be solved. This leads into the goal of exploration, which is to know the environment with all its hidden caves and private rooms, isolated cities and underwater temples, and where you must go to apply the knowledge you've gained to acquire the thing you currently desire.
I'm sure this all reads as exceptionally vague, and different people will interpret it in different ways, finding different implied goals in it. That's exactly the point, though. The best goal a MUD (or any game) can have is to allow players to make their own goals. Of course, they're all still variations on a smaller subset of goal archetypes - primarily exploring and acquiring. It all goes back to the classic example of the four types of players who play MUDs (Bartle): Explorers, Achievers, Socializers and Killers. It's fairly self-explanatory as to what interests drive each of those types, and almost everyone is going to be some mixture of the types. As I've already stated, my game focuses on the explorers and the achievers (acquiring). Socializers are still welcome (and prevalent) - they just aren't included in this discussion because it's difficult to design goal driven socializing. The Killers are catered to with goals along the lines of defeating an exceptionally strong boss or fending off numerous AI controlled attackers. However, I understand this isn't in the spirit of the general interpretation of a 'Killer', which leans more toward PvP competitiveness. In that respect, they are unfortunately disfavored, as Killers tend not to play well with Socializers and Explorers.
My game (when closer to being finished) will be sortof along the lines of what Lyanic described for 7th Plane except that I've not only catered to the Explorers, Achievers and Socializers but also to the killers by providing goal based PvP in addition to the explorative nature of the world. Players will also end up needing to craft some of their gear if they want to get their hands on some of the better stuff as well.
Cyra will center around two or three factions vying for the possession of artifacts, whichever faction possesses the artifacts gains certain bonuses to skills and abilities. In truth, the players don't care about the bonuses as much as they do about 'being on top' and holding all of the artifacts, this gives them a reason to juggle them back and forth. The goal will be to make group fights memorable and have that be more of the concentration as opposed to solo PvP. This is accomplished through the use of siege equipment, field construction, and ranged attacks that reach from room to room such as artillery type magic spells, archer volleys, and constructed items like catapults.