This particular artifact has caught my attention. I can barely find any lore pertaining to it. It has a blurb about how it was used by Zagig and Iggwilv to imprison Fraz-Urb'luu in Greyhawk but that's the only thing about it I can find.
Is there anything else I missed, or, is this just a Maccguffin or a Deus ex Machina?
1 Answer
There doesn't appear to be much
The Ichor Lance itself only seems to be mentioned in two publications, as far as I can tell, and neither of those describes the artefact or any properties it might have in any detail.
It first appears in the Dragon #333 (July 2005) article "Demonicon of Iggwilv: Fraz-Urb’luu", which is also the first publication to describe the events of his imprisonment in any detail; prior to this, he'd simply been described as having been imprisoned under Castle Greyhawk for some time before being released, and the question of how he got there in the first place was left unexplored. Though the Ichor Lance is mentioned, there is no description of its powers; in fact, in this telling of the story, its actual powers aren't even relevant! It is only used as bait by Zagig to get Fraz-Urb’luu to use his Disjunctive Touch power on an artefact, which has a chance of backfiring on him and stripping him of his powers.
[...] the wizard confronted the demon with a powerful artifact known as the Ichor Lance in an attempt to carve away a portion of his fiendish essence. When Zagig tried to use the artifact on him, Fraz-Urb’luu took it in his hands and disjoined the artifact’s power.
Yet something went wrong. As the artifact’s magic was torn away and ruined, Fraz-Urb’luu felt the same force rebounding into his own being. In an instant, his powers were stripped from him, and Zagig’s true purpose became clear. The Ichor Lance was simply bait, and now that Fraz-Urb’luu had taken it, Zagig had no problem using his magic to imprison the Prince of Deception in a massive stone bas-relief deep within the dungeons below Castle Greyhawk.
[...]
Even artifacts are subject to his disjunctive touch, although there is only a 20% chance of actually affecting such powerful items. Each time Fraz-Urb’luu destroys an artifact he must make a DC 25 Will save or lose all spell-like and supernatural special attacks and special qualities for 100 years.
In the subsequent 3.5e sourcebook Fiendish Codex - Hordes of the Abyss (2006), the Ichor Lance is mentioned again but even less detail is provided:
Instead of assailing him in the impregnable fortress of Hollow’s Heart, Fraz-Urb’luu’s rivals indirectly aided one of the demon’s enemies, the archmage Zagig Yragerne. Using a demon-provided artifact called the Ichor Lance, Zagig bested the Prince of Deception in battle on the Material Plane, binding him to a bas-relief in the dungeons of Castle Greyhawk for more than 200 years.
But besides that, the Ichor Lance doesn't seem to be mentioned again in any published texts. The 3.5e adventure module Expedition to the Ruins of Castle Greyhawk (2007) mentions that Zagig imprisoned Fraz-Urb’luu with the help of the witch Iggwilv (AKA Tasha, of Tasha's Hideous Laughter), but omits the Ichor Lance. Interestingly an "ichor" theme is still present, since the adventure expects the party to visit Hollow's Heart, the layer of the Abyss ruled by Fraz-Urb’luu, and specifically a location therein called the Ichor Shrine - but there doesn't seem to be any actual link between the Shrine and the artifact.
The history of Fraz-Urb’luu's imprisonment is brought up again in a few places - for example, the 4e-era Dragon #414 article "History Check: The Iggwilv–Graz’zt Affair" again describes how Iggwilv and Zagig worked together to imprison Fraz-Urb’luu, but the Ichor Lance is nowhere to be seen. In 5e material, Fraz-Urb’luu is described briefly in both Out of the Abyss and Mordenkainen's Tome of Foes, but they only say he was imprisoned under Castle Greyhawk and omit any details about how that happened.
It appears that the Ichor Lance was introduced as a macguffin without description in the 3.5e-era and then quickly forgotten about. The best we could guess about any powers it had would be that it might have been able to "carve away a portion" of a fiend's essence, but it isn't actually used to that effect and it's unclear whether or not that was what it actually did.