Ogremoch
Ogremoch, also known as the Prince of Evil Earth Creatures or Elemental Earth, the Master/Lord of Black Earth, and the Stone Tyrant, is one of the five iconic Archomentals of Dungeons & Dragons, having been created by Gary Gygax for the Fiend Folio alongside Imix, Olhydra, Yan-C-Bin, and Cryonax. Of all the Archomentals, he has probably fluctated the most of the four editions in which he has appeared.
1st Edition
Described as resembling a 10ft tall "rough and unfinished humanoid" made of stone and clay - his attendant pic looks like a child's crude clay sculpture of a man; a rounded blobbish figure with cylindrical near-tentacles for arms, stumpy legs, and shallow depressions for eyes and a downturned mouth - we know pretty much nothing about him other than he claims rulership over all of the malevolent creatures on the Plane of Earth and he lives on a "great flat-topped mountain" on that plane. But that's hardly surprising; this was the Fiend Folio, and space for monster lore was pretty limited.
2nd Edition
In 2nd edition, Ogremoch appeared in the Monstrous Compendium Appendix 3 for Planescape alongside not just his former brothers & sister, but also a cast of four new good archomentals: Ben-Hadar, Chan, Zaaman Rul and his new personal rival, Sunnis.
This version of Ogremoch was a lot more fleshed out... but still not exactly brimming with information. Described as a 10ft tall rocky tyrant, whilst he dwelles within a fortress atop a giant plateau inside of an immense cavern in his home plane, he spends much of his time wandering the Plane of Earth looking for new subjects to intimidate, new slaves to command, and new opponents to challenge. Brutal, cruel and wicked, fear of Ogremoch drives many of the plane's natives to Sunnis for protection, leading to legendarily destructive battles between the two.
This version of Ogremoch got a physical revamp and was a lot more intimidating than the child's crude clay doll of 1e; a lanky, scowling, humanoid figure, whose skull grows into a rocky crown.
3rd Edition
Dragon Magazine #347 gave us the most insight into Ogremoch - and the rest of the Evil Archomentals - of any edition before it. His home turf is still the "plateau in a cavern" of 2e, but it now has a name; Stonemire. Swelteringly hot, it's reputed that Ogremoch has buried many of his defeated foes inside the mesa - some of them supposedly even alive so that he can feed on their powers in some way. He still prefers to spend most of his time roaming the plane looking for creatures to bend to his will or destroy.
Now we finally get a look at how Ogremoch thinks; callously practical, industrious and prudent, with a personality marked by its rigidity. Dispassionate, but still thoroughly evil, Ogremoch relishes in violence and brutality - in fact, in this edition, he abandoned his "traditional" rivalry with Yan-C-Bin, deeming the evil air Archomental to be too flighty to act as a proper rival, and instead focuses his wrath on Sunnis. He's also a great planner and schemer, although his focus on thinking in the severe long-term - the phrase "three schemes beyond the current one" is used - means he tends to confuse enemies and allies alike, giving him a reputation as a dull-witted and slow-minded incompetent. Anyone stupid enough to buy that will usually end up squashed to a pulp.
Among other changes in this edition, we learn that Ogremoch fought on the side of the demons with the Queen of Chaos during her battle against the Wind Dukes of Aqaa - mostly because, at the time, Ogremoch was fighting Yan-C-Bin and he had chosen to side with the Wind Dukes. He still bears a deep grudge against the Wind Dukes and is eager to settle the score against their allies. He's also the eldest and the most powerful of the evil Archomentals, and has been planning to get rid of his siblings since before they even came to exist - talk about sibling rivalry! His greatest ambition is to seize control of the Great Dismal Delve, a region controlled by the Dao genies and which is riddled with planar portals - fortunately for them, the dao are currently strong enough to hold Ogremoch at bay, forcing a reluctant truce.
Ogremoch's cult includes, aside from the obvious earthen Elementals, subterranean races like dwarves, gnomes, stone giants, gargoyles and trolls. His holy symbol is an equilateral triangle with short hash marks through each leg, and his unique "Avatar of Elemental Evil" is the Black Rock Triskelion (Monster Manual IV).
3e's version of Ogremoch built upon 2e, tweaking some fine details but mostly preserving him from his past edition.
4th Edition
4th edition changed Ogremoch. A lot. For starters, he went from his classic 10ft tall (Large) height to a Gargantuan, near-shapeless abomination of quaking stone, who turns the very earth around him into a bloodthirsty extension of his being. He also regained his original home of a great flat-topped mountain, as the Elemental Chaos is different to the Elemental Planes, except that now he's a prisoner there, entombed by chains that Moradin forged with "the whipping winds that range in the heart of his mountain home".
Ogremoch's cult is now incredibly diverse, and in part that's because there are many different interpretations of him. Some worship him as the same old cthonic monster. Others, more cerebral, worship him as the lord of mysteries and secrets, as master of hidden places and dark moist earth and of the creatures within it. Others worship him because being lord of earth means he claims dominion over the earth's hidden treasures - gold, silver and gemstones, to name a few. Thus, in 4e, Ogremoch's cult includes everything from hedge witches to troglodyte hordes to greedy prospectors, avaricious miners, and dwarves.
In 4th edition, Ogremoch is regarded as the patron god of the Norkers, a stony-skinned race of goblinoids.
5th Edition
Ogremoch's first appearance in this edition was as a mention in the Monster Manual, where it's stated that gargoyles were created by him to mock and destroy the air creatures he so hates.
Like his hated siblings Imix, Olhydra and Yan-C-Bin, Ogremoch returns as one of the bigger bads of the adventure "Princes of Elemental Evil", which is all about the party getting involved in the four warring cults of elemental evil dedicated to the four malevolent archomentals. In this edition, Ogremoch is described as a 50ft tall shambling colossus of animate rock shot through with crystalline growths. His character is slightly tweaked; whilst still an overbearing tyrant who wishes to crush and subjugate all others, and to outlast those he cannot defeat, he also gained a new characteristic of being a miserly bastard who regards all of the treasures of the earth as his own sovereign property.
Because of this, not only can Ogremoch sense whenever anyone removes nuggets of precious metal or raw gemstones from territory under his influence, but he also despises anyone who dares to shape or build things from stone. Extracting treasure from the earth is anathema to this malevolent archomental, and as such, whenever he gains access to the Prime Material, Ogremoch's presence is signaled easily by his habit of methodically locating and destroying every mine, quarry, town and fortification in his reach.
In a neat little reference to the Monster Manual, one of Ogremoch's Legendary Actions in this edition is to sacrifice 50 hit points to create a gargoyle.