Far Realm: The Root of All Evil . . . Sort Of
The following material presents my view of the Far Realm as the root of all evil . . . sort of. I will debunk certain myths and tie together a wholistic understanding of the role that the Far Realm has played in the state of evil throughout the known planes.
To begin, I will clarify that the Far Realm is not the cause of all evil. It is, however, the source of some of the most evil phenomena known to all. Let's take a look at how this all began.
HOW IT ALL BEGAN
We know that the breaching of the Living Gate ("that once barred the Far Realm from the Astral Sea," Psionic Power, page 95) was the first intrusion of the Far Realm into the known planes ("the original gateway through which the Far Realm breached the Astral Sea," The Plane Above, page 95) (" . . . the shattered Living Gate, which provided the Far Realm's first entry into the Astral Sea . . ." The Plane Above, page 63) (" . . . all agree that the Far Realm broke into the cosmos as a consequence of the destruction of the Living Gate," The Plane Above, page 63).
We also know that three gods were responsible for the destruction of the Living Gate: "Pelor, who shined light into all shadows, first found the gate, though he later wished he had not. Ioun, whose mind hungered to understand all things, awoke the sleeping gate. And a third, nameless god, who feared no danger and doubted all authority . . . ." (Player's Handbook 3, page 4). What many do not realize is that the third god was Tharizdun (see below for further detail). Together, the three gods defeated the guardian of the Living Gate (Pelor and Ioun propagandists later laid blame of the slaying solely upon the shoulders of the third god, but how could a single god defeat a "powerful being, said to be neither god nor primordial but kin to both" (Player's Handbook 3, page 4)?), but it was Tharizdun alone who shattered the Living Gate.
Eons prior to the shattering of the Living Gate, beings of evil incarnate, known as the obyriths, discovered a barrier between their realm and another, and sought to breach it (Demonomicon, page 7). Their realm was the Far Realm and that barrier was the Living Gate. Despite millenia of effort, focusing all of their will and energy towards a singular point within the Living Gate, the obyriths could not succeed in breaching the barrier until they received the unlikely assistance of three gods on the other side of that barrier. When Tharizdun shattered the Living Gate, he came into contact with, and instantly became swayed by, the shard of the shattered gate containing that singular mote of utter evil ("The touch of the shard drove this god to madness, corrupting him so completely that he was no longer recognizable as his former self." Monster Manual, page 52).
"Ioun and Pelor are credited with sealing shut that fell gateway to the Far Realm, but not before reality had been corrupted" (Psionic Power, page 108). Ioun’s power continues to hold the portal closed (Player's Handbook 3, page 12) and "Pelor secretly preserves the largest fragments of the Living Gate within his inner sun beneath Hestavar" (The Plane Above, page 63).
Perhaps, you are wondering what a single breach to the Far Realm has to do with the most evil phenomena known to all? Take note of what follows.
THE FAR REALM BRINGS EVIL AND CORRUPTION TO THE ELEMENTAL CHAOS
Consider what we know of the Elemental Chaos. "Most of the inhabitants of the Elemental Chaos share a primal drive toward entropy. Many are creative in their own ways, building structures and civilizations, tearing them down, then beginning anew" (Manual of the Planes, page 62). The primordials are "ancient forces of creation" (Manual of the Planes, page 70). They are "raw, untamed chaos in elemental form, almost indistinguishable from the plane that birthed them" (Manual of the Planes, page 70). "They exist solely to act out that cycle" and "most are unaligned" (Manual of the Planes, page 70).
As we know, Tharizdun carried the shard of utter evil to the Elemental Chaos and embeded it there (Monster Manual, page 52). When Tharizdun planted the shard, it "unleashed power like that realm had never seen before," momentarily permitting the obyriths entry into the Elemental Chaos (Demonomicon, page 7). The evil of the shard "took root like a foul seed of corruption, burrowing deep into the unshaped matter of the Elemental Chaos and spreading unholy tendrils far and wide. A yawning chasm of infinite gloom and despair opened up at the lowest pit of creation, swallowing all matter and light, defiling anything that drew near." (Monster Manual, page 52). Thusly was the Abyss born, and demons soon thereafter.
The Abyss has been described as " a hole in reality at the bottom of the Elemental Chaos" (The Plane Below, page 108), a "festering cyst beneath the Elemental Chaos" (Monster Manual, page 52). " The evil of the Abyss corrupted even some of the mighty primordials—Demogorgon, Baphomet, Orcus—and reshaped them into the likeness of pure destructive evil" (Monster Manual, page 52), what we call demons. "Demons are the tools the Abyss uses to extend the reach of its obliteration" (Manual of the Planes, page 68). They "possess shapes as diverse as anything in the Far Realm" (Demonomicon, page 10).
We see that the single largest amalgamation of evil in the entire Elemental Chaos is attributable to the influence of the Far Realm. Next, we look at the Astral Sea.
THE FAR REALM BRINGS EVIL AND CORRUPTION TO THE ASTRAL SEA
Pazuzu, an obyrith in the Abyss, manipulated Asmodeus into succumbing to the evil of the shard (Demonomicon, page 9). Asmodeus "sought out and found the shard in the Abyss's incalculable depths" (Demonomicon, page 9). He "stole away a sliver of the shard" and forged it into "a ruby-tipped rod of incredible power"" (Demonomicon, page 9). "Armed with his scepter of absolute evil, Asmodeus led an invasion of the Astral Sea" (Demonomicon, page 9) and used his fragment of true evil to slay his divine master (Manual of the Planes, page 89) (see also Monster Manul, page 60). "Asmodeus had grown too strong for his enemies to overcome without causing destruction on a planar scale" (Wizards Presents Worlds and Monsters, page 76).
Similar to the Abyss, we see that the Nine Hells of Baator are attributable to the influence of the Far Realm. Lastly, let us observe the natural world and its echoes.
THE FAR REALM BRINGS EVIL AND CORRUPTION TO THE NATURAL WORLD AND ITS ECHOES
"In places where cosmological boundaries have become too thin, Far Realm influence sometimes seeps in, staining reality in terrible ways. At the edges of such contact, a subtle influence pervades the area, overlaying the landscape with an unnerving sense of dread, and foisting nightmares upon those unlucky enough to rest within or nearby. At its heart, the landscape is distorted, with flora and fauna dramatically tainted. Strange new creatures, equal parts nature and madness, fester and hunt" (Manual of the Planes, page 78). "Where stray emanations from the Far Realm leak onto the world, matter stirs at the beckoning of inexplicable urges, then burns to ash or takes on monstrous new life" (Manual of the Planes, page 30). "When these rare intrusions occur, the warping pressure of the Far Realm transmutes previously inert substances. This blending of realities results in horrifying corruptions, disruptions, and sometimes even the birth of squiggling aberrant monstrosities" (Manual of the Planes, page 30).
As a consequence of the Far Realm's evil and corrupting intrusions, the known planes have directly responded in several ways: from the spontaneous creation of psionic power ("[psionic] power is the world's response to the intrusion of the Far Realm" (Player's Handbook 3, page 5)) to the birth of entirely new races. "The wilden emerged from the unspoiled reaches, ancient bogs, and primeval forests of the Feywild. Awakened to fight the growing corruption plaguing the land, they strive to restore the natural order and to purge aberrant horror from the world" (Player's Handbook 3, page 15). Shardminds "consider themselves to be energy creations . . . of the [Living] Gate. The three major shardmind philosophies (Player's Handbook 3, page 13) agree that the way to seal the Far Realm away forever is to rebuild the Living Gate" (The Plane Above, page 63). Shardminds "seek to rebuild the gate and forever cut off the Far Realm’s ability to influence the world" (Player's Handbook 3, page 12).
As I have already conceded, the Far Realm cannot be blamed for all of the evil in existence; but, it is responsible for the Abyss, the Nine Hells, an entirely new power source and the consequent existence of several races.