Here is an oldie from the ATOT vaults...
FAQ: On Moderators
Categories of Moderators
Common Moderators are the smallest, and most prone to gathering in numbers. They might be encountered as small groups of Moderators living in subterranean regions (often called Cave Moderators), or as entire communities. In forums where Moderator nations exist, it is likely that these are made up almost exclusively of Common Moderators, though some settings may have Great Moderators and Common Moderators living alongside each other (Great Moderators being those Moderators who for some reason just grow bigger, possibly because they have eaten more unruly forum users).
Great Moderators are bigger and meaner, but slower, and with a tendency to follow their bestial instincts. In the most common approach, they tend to be more solitary. They tend to live in remote isolated regions, and often possess a magical ability to harness or manipulate the environment in which they dwell. They make huge nests from banning-sticks, and line the nests with troll fur. Great Moderators are seldom sources for "Mod quotes", since most of their remarks scare the pants off of anyone with half a brain.
Water Moderators: In many settings, Swamp Moderators will not exist - perhaps the Water Moderators have eaten them all. This breed of Moderator deserves a special category all its own - Water Moderators are as smart and cunning as any human, and possess the strength and might of a Great Moderator and, of course, a predilection for locking threads and making smart-alecky remarks about it.
In some settings, the difference in size and ability between Common and Great Moderators are merely quirks of birth - all may coexist within the same society (in a similar way to Tolkienesque Orcs and Uruk-Hai). Some experts view Water Moderator as simply a sub-class of Great Moderator. Many of these experts have been banned and/or eaten.
The Ecology of a Moderator
Moderators are intelligent and magical creatures, and can learn to exploit their chosen habitat - those living in swamps often learn powers to manipulate swamps, for example, and so are thought of as a separate breed than those Moderators who take up residence in a forest (or, for that matter, in the Hot Deals Forum). But if that swamp-dwelling Moderator were to be forced to move home, and settled in a mountain range for instance, nothing would stop him from acquiring new powers more appropriate to his new habitat. All Moderators are essentially the same beasties, though - like humans - they may specialise in different areas. And some smell better than others.
Common Moderators (better known as Cave Moderators) are generally regarded as the weakest of Moderators; what isn't generally recognised (often even by Moderators themselves) is that such Moderators are, in fact, the juvenile form of all other Moderators. Highly communal in nature, these Moderators often form violent societies and warbands. Where nations of Moderators exist, they are usually comprised almost entirely of Common Moderators. Life is often short, even for these powerful creatures - but for those who live long enough, a strange fate awaits.
Even the wisest of Moderator shamanesses can't predict when it will happen, or even if it will happen to a particular Moderator, but when the Curse strikes, there's no resisting it. The Afflicted Moderator experiences a growth in his hunger for trollish flesh, driving away all reason. Moderators generally need little provocation to fight each other, but the Afflicted face a constant battle with their hunger even in the presence of other Moderators. Sooner or later, they lose control. They are soon either killed, driven out of the community or flee into the wilderness on their own initiative... Sometimes they just get ticked off and ban the bejabbers out of each other.
Great Moderators (Wood, Mountain and Swamp): These Moderators seek out isolated places to make their home, deep in the darkest forests, the harshest mountains, the most treacherous swamps, the For Sale/Trade Forum after midnight. They make themselves a secret lair, venturing out to prey upon any creature who crosses them. From time to time they lose control utterly, their destructive rampages mistaken for the eruption of a volcano or Roseanne Barr passing gas. This solitary life is initiated by a change in the Moderator, a growth in its irrational, bestial side. But Great Mods are not always solitary; they sometimes band together in groups of 2 or 3, always of the same type (Swamp Moderators do not mix with Mountain Moderators, etc.) They may have some ability to seek out powerful family members - as in the cases of Grendel and his mother, or Melissa and Joan Rivers.
The Moderators known as The Great Old Ones are very rare indeed - most Moderators never make this transition. They are either killed by other Moderators, annoyed to death by trolls, or lose control of their hunger and make mistakes which lead to their demise. Some fall victim to a more mysterious fate (perhaps truly becoming one with the environment they inhabit, perhaps migrating to ArsTechica and mere oblivion).
Final Note: Moderator Singularities
Moderators are not easy classifiable. Moderators, especially older Moderators, might display unusual attributes or powers, even extra heads! (Case in point: the AnandTech Administrator).