Urakia is a campaign setting for Dungeons and Dragons. The game is d20 compatible, but the game introduces unique rulesets, classes, and races.  

The world was forged on the bloodshed of endless battles waged by Gods who vie for control of the heavens and pit mortal against mortal to sway the balance to their favor.

Age upon age, this savage history has repeated itself. But at the dawn of the Fourth Age, a new threat looms on the horizon. Over twenty years has passed since the Great Sundering, when the world lost its magic. 

The Sundering has come and gone. The short sighted rejoice in the return of magic, while the wise grow cautious. 

Soothsayers, seers, and prophets warn that this is only the beginning. The wicked rally and plot to benefit from any such disaster, while the benevolent seek to prevent it. Where will your allegiance lie in this inevitable cataclysm? 

U5: Urakia Campaign Setting 5th Edition

The Urakia campaign setting was originally created in 1988 as an alternative campaign world for players who liked to wield a lot of power. The primary aspect of the game was to give the monsters more power, and give the PCs enough power to survive. Originally designed for 1st edition AD&D, "Urakian Adventures" was designed to still challenge the high level character considering retirement, while offering new PCs a great amount of power to survive.  

The rules at first were rough and didn't make a whole lot of sense. Second Edition Urakian Adventures was made to fix these rule problems. For example, warlocks had a spell pyramid in addition to having spell points, which didn't make a lot of sense. Also, a half demon female was always a succubus and a male was always a Cambion, even though the rules stated that an Alu-demon was the offspring of a Succubus and a human. The new rules compensated for female Cambions, in case of a non-Succubus demon mother, and male Alu-demons, in case the father was an Incubus. These and other changes transformed second edition into something that made a lot more sense. 

When AD&D second edition came out, new charts were made for Urakian Adventures to simplify things as TSR had done.  One thing AD&D 2nd Edition did was boost the power of their own monsters. To keep up with the "greater firepower" aspect of Urakian Adventures, the monsters there were upped in scale too. These changes marked Urakian Adventures 3rd Edition.

U4E, or Fourth Edition, was a hybrid of both AD&D 2nd Edition and Dungeons & Dragons 3E. It was made with two principles in mind. First, there were a lot of D&D players out there at the time that had been playing the game for over a decade and a half. Not all of these people were going to run out and buy the new books. The second reason was that Urakian Adventures should not be made obsolete by the new rules. In short, the hallmark of Fourth Edition was that it was both 3E and 2nd Edition compatible. 

U5 is the Fifth Edition of the game, simply known know as "Urakia". It is purely d20 / D&D 4th edition compatible. It also streamlines the race and class selections and modifies some of the setting itself.