Arduin was both the name of a series of role-playing supplements, and the name of the world they were set in, both created by David A. Hargrave starting from 1977 until his death in 1988. Arduin was one of the first - or at least best-known - early examples of what might be called "Gonzo" fantasy - a sort of anything-goes, all-inclusive melange of mythpoetic madness that shamelessly borrowed from nearly everywhere, and when it ran out of stuff that wasn't nailed down, trekked into the wilds of imagination - drug-induced or otherwise - to fill in gaps and plasterboard over the worst holes in the narrative.
The result was a roller-coaster ride of races, spells, poisons, monsters, weird weapons, classes, rules extensions, world details, religions, gods, demons, and a plethora of strangeness that nearly any dungeon master could find something to love in - all painstakingly typed up on a typewriter and laid out in digest-sized handbooks (8 of them), with artwork pasted in from the likes of Erol Otus and Michio Okamura.
Very little of Arduin has directly made it into Malaster - it's a little too gonzo, in some respects, for my current play style. But to say that Arduin has not informed and inspired nearly everything I do in gaming would be incorrect. So there is, perhaps, a little Arduin - if only because of its inspirations - in Malaster.
The Blind Idiot God. The Daemon Sultan, who dwells at the center of the universe, kept sleeping by the mad piping and drums of unseen tormentors. In this case, Azathoth stands in for all of the Cthulhu-esque madnesses of the Great Old Ones and their many-angled servitors.
Cthulhu and Swords&Sorcery fiction are nearly tied at the hip - many of the writers of Lovecraftian fiction and pulp fantasy drew from the same inspirational progenitors (Lord Dunsany, for example), merely in different directions, and many of the early writers - Clark Ashton Smith, HP Lovecraft, and Robert E Howard, for example - were close friends, shared frequent correspondence, and even collaborated on plots and world-building. It is not surprising, therefore, to find references to Lovecraftian horrors in some of Howard's works, for example, and to see suggestions of Hyperborea and Atlantean excesses in some of Lovecraft's writings (and such ties were much more strongly suggested - or even outright stated - in the works of those who would come after).
But a little - or even a very little - Lovecraft can go a very, very long ways in a fantasy game. Too much, and it begins to dominate the plot landscape very quickly, overriding nearly everything else. SO hints and suggestions that Things Man (and Elf and Dwarf) Were Not Meant To Know certainly can be found - but players are unlikely to spend much time seeking out the thin melodies of mad pipers who cast their somnolence upon the Nuclear Chaos.
Atlantis serves many purposes in fictions of the fantastic. It is the lost utopia, the advanced civilization that fell because of hubris, or decadence, or invoking the wrath of the gods. It can be a threat from beyond time, a source for amazing treasures, or sciences, magics or miracles long-lost - or all of these things. Númenor is Atlantis, in a sense - so is the Dragon Shogunate, or the First Age, in Exalted.
There are several Atlantis stand-ins in Malaster. The most obvious, of course, is the Old Countries - the lands that many/most Malastrians fled from two centuries ago, in the face of some mysterious threat so horrible few can even agree on its nature, let alone wish to speak of it. But Malaster itself has its Atlanti - the terrible Secret Kingdoms of the Sarastian Empire, the proud realms of the Acanti, the demon-infested horrors of the Maras-til. Little is known of these strange principalities of yesteryear - indeed, to some scholars they are little more than myth and conjecture. But even through the millennia, they cast their shadows over the current inhabitants....