In the Ultima series of games, the Gargoyles were another race of creatures that once inhabited a world parallel to that of humans in Britannia. They are a much wiser and older race than the humans are, and it is they who had originally summoned the Codex of Ultimate Wisdom from the Ethereal Void. In Ultima IV, the Avatar descends the Stygian Abyss into what turns out to be the Gargoyle Temple of the Codex and brings its knowledge to the Britannians.
Shortly afterwards, the greatest mages of Britannia begin an effort to raise the Codex from the Abyss into the Shrine, in the process creating a vast Underworld into which Lord British becomes trapped by the Shadowlords in Ultima V. The Underworld collapses at the conclusion of Ultima V, destroying much of the Gargoyle world in the process.
By then, the Gargoyles were desperate, and decided that their ancient prophecies regarding a False Prophet were fulfilled by the Avatar, and the prophecies further stated that the only way to avert the prophecies, which spelled utter extinction for their entire race, was to sacrifice the Avatar. At the start of Ultima VI they trick the Avatar into entering what is left of their realm and prepare to begin the sacrifice, but are prevented by the timely intervention of the Avatar's companions. The rest of Ultima VI concerns the Avatar's attempts to find a way to forge a lasting peace between the two races.
In Ultima VII, the Gargoyles have settled in diverse places across Britannia, and are the subject of prejudice and oppression all throughout. Their rich culture is endangered by the encroachments of the Fellowship.
Physically, gargoyles are large, red-skinned creatures, with horns and skull-like faces. They present a demonic appearance to ordinary humans but they are far from evil. Anyway, they are no more evil than humans can be. Two castes of gargoyles exist, winged and wingless. The former were the ruling class in the original Gargish society, having the ability of speech and abstract thought. As originally presented in Ultima VI, the wingless gargoyles did not have the ability to speak, were physically and mentally inferior in all ways to the winged, and yet were cared for and protected as full members of gargoyle society.
The Gargoyles also had their own version of the Eight Virtues based on different principles from that of the human Virtues: the principles of Control, Passion, and Diligence. They extolled Mondain, Minax, and Exodus, the three villains of the first Ultima trilogy as embodiments of these principles.
As presented in Ultima VI, the gargoyles reproduced asexually, and this fact is borne out by the detailed Latinesque language that was invented for them: there are no pronouns in their language (Gargish) that denote the gender of the subject. A strange, contradictory departure from this fact which all other Ultimas that referred to Gargoyle society concur with is seen in Ultima IX, which shows a Gargoyle "queen". The natural lifespan of a typical Gargoyle is much longer than a human's, as Naxatilor the Gargoyle seer is said to have lived more than a thousand years, and the Gargoyle king Draxinusom lived from Ultima VI to Ultima VII, a span of 200 years.
Gargoyle society as it existed in their destroyed world was egalitarian, and no concept of money or of property ownership existed before they migrated to Britannia at the end of Ultima VI. Whatever one needed, one was given. It seems that only after exposure and tentative integration with Britannian society were these notions brought into their minds.
The Gargoyle warriors also took the venom of a silver serpent as a powerful stimulant that caused them to become berserkers in battle and nearly unstoppable killing machines. The drug has somewhat different effects on humans as was presented in Ultima VII, where it became a social problem.
Sources: mostly Ultima VI and Ultima VII.