[Pam Korda, Leigh Butler, Jennifer Liang]
The Gholam seems to be the hardest-to-kill monster RJ has introduced thus far. What, exactly, is it? We have information on it from Birgitte, who has some memories of the War of Power [ACOS: 40, Promises to Keep, 606-607], from Elayne, Mat, etc.'s encounter with one in [ACOS: 39, Six Stories, 598-600], from the short gholam POV scene in [TPOD: 2, Unweaving, 84-85], and from Mat's second duel with it in [WH: 16, An Unexpected Encounter, 353-355].
Gholam were created by Aginor [LOC: 23, To Understand a Message, 347] for the express purpose of killing channelers, although they're pretty handy at killing non-channelers, as well. The OP can't touch them; the effect of channeling at a gholam is exactly the same as channeling at a person wearing Mat's foxy medallion (i.e. the flows break apart on contact). Furthermore, they are immune to conventional weapons, too: nobody is able to harm the one who Mat fights with swords, etc, and the gholam itself thinks "it had never encountered anything that could harm it. Until that man with the medallion" [TPOD: 2, Unweaving, 84]. They can sense the ability to channel at a distance of about 50 paces, and they can detect use of the OP at greater distances (it felt the channeling at the Kin's farm in TPOD). They look like normal human beings on the outside. Inside is another matter. They have no bones, and can squeeze under a door, and are very strong, and very quick. Only six were ever made; three have a masculine outward appearance, three feminine. They appear to be at least as intelligent as Fades (Mat chats with the one he fights in Ebou Dar), and they are living things, not some sort of machine. (Mat surmises (actually, Birgitte surmises) that the one they met was "kept alive" since the Breaking in a stasis box.)
They feed on blood; the Ebou Dar gholam refers to its victims as "those I harvest" [WH: 16, An Unexpected Encounter, 355]. There is some way to control a gholam, and force it to do one's bidding. The Ebou Dar gholam thinks: "The one who commanded it wanted [Mat] dead.... for the time being, it was constrained. For its entire existence it had been compelled to obey one or another human, but its mind held the concept of not being constrained" [TPOD: 2, Unweaving, 84-85].
There is some contention over the nature of the gholam's exact physical makeup. Most people subscribe to the "liquid gholam" theory (a la the T-1000 in Terminator 2: Judgment Day). RJ's choice of words in various descriptions of the gholam seems to suggest this ("Fluid as quicksilver", "flowed aside like water", etc.). It's not specifically said, but there is the intimation that the knife wounds Mat gave the gholam in ACOS closed up instantly; they didn't bleed, at least. The gholam do seem to be more limited than the T-1000, in that they apparently can't assume any form, only liquid form and their humanoid form. (If not, why specify that three are male-shaped, and three are female-shaped?) Stemming from this theory is the assumption that a gholam would be able to reattach a severed body part or parts.
Not everyone buys this theory, though. The description we have only says that the gholam have no bones, not that they have no internal organs or support structure at all; as Ben Elgin points out, "Mice can collapse their skulls and ribcage... Cartilage explains the traversal just as well." There is also no real reason to assume that the gholam can reattach a severed body part, other than that the T-1000 could.
Where have we seen gholam? We've seen two for certain, namely the one in Ebou Dar, and the one that killed poor Herid Fel in Cairhien at the end of LOC. There is one previous possible gholam encounter, which took place "off-screen." This is the killing of Lord Barthanes in TGH. Barthanes was clearly killed at Ishy's instigation because he helped the renegade DF, Padan Fain, get away with the Horn of Valere. Barthanes died in a very similar fashion to Fel, i.e. he was ripped limb-from-limb. Furthermore, this took place in the same building as Fel's demise. Again, this may or may not be a gholam-induced death, but it is worth mentioning as a possibility.
The only thing we know for certain that can injure a gholam is Mat's foxy medallion. When Mat smacks the Ebou Dar gholam with it in [ACOS: 38, Six Stories, 598], the gholam is burned-- "The medallion fell across the man's cheek. The man screamed. Smoke rose around the edges of the foxhead, and a sizzle like bacon frying....A raw red brand marked where the foxhead had fallen." Later in WH, Mat burns the gholam several more times with the medallion. What we do not know is why the medallion hurt the gholam. There are two possibilities:
Both the medallion and the gholam have the unusual property that they somehow neutralize flows of the OP. (Note that the actual mechanism employed by each may be different.) It is possible that some kind of adverse reaction occurred when the medallion came into contact with the gholam's body. While the medallion didn't get characteristically cold, it did seemingly get hot.
It is difficult to be more precise, because we don't know how either the medallion or the gholam actually work. Perhaps it is because the gholam are made with/are held together with/have some connection with the OP, and the medallion negates the OP. Or, perhaps it's a "like charges repel" sort of deal. Or, maybe the gholam is a kind of "living ter'angreal," and the effect is due to an adverse reaction between similar ter'angreal, as described in [TDR: 23, Sealed, 217]. If it is the case that the magic is the key, then a gholam could probably be killed by prolonged contact with some weapon/ter'angreal made to copy the medallion's effect.
An argument against the theory that the medallion's ability to negate flows is the key, is that then the gholam probably would have been hurt by contact with Mat himself, and not just the foxhead. [James Huckaby] Then again, maybe not. As stated above, we don't really know how the medallion works. It was pointed out that when Mat was wrestling the gholam, the foxhead fell out of Mat's "open" shirt: "Struggling for air, he [Mat] pushed himself up, foxhead dangling from his open shirt." [ACOS: 38, Six Stories, 597] So, if the medallion works only when it is in contact with the wearer, then Mat may not have been in contact w/ it when he touched the gholam. [Jason Wilson] Of course, this objection does not apply to the idea that the reaction was due to the "similar ter'angreal interference" effect.
The medallion is made out of silver [TSR: 26, The Dedicated, 306-307], and this is the key to its anti-Gholam capabilities. The argument for silver is more of an argument against the medallion's magical properties, combined with some cross-pollination from werewolf and vampire legends. It is not likely that the foxhead works because it is destroying flows, because the foxhead doesn't get cold after damaging the gholam, it just has "the cool of silver" [ACOS: 38, Six Stories, 598]. Loony idea: When the gholamstuff and silver come into contact, there is a chemical reaction. This reaction is exothermic--the heat is produced by the reaction, not by the medallion.
An argument against this theory is that it seems kind of silly. Why would the Forsaken make such specific, deadly anti-AS assassins if they have such a common, easily exploitable Achilles' heel? Why would the Forsaken be so wary of them that they limited their number to six? [Tim Yoon]--"Oh No! A gholam's chasing us!" "How much money do you have on you?" [Aaron Bergman] The former question can be rationalized by saying that the Forsaken counted on the fact that people wouldn't think to use silver on something the OP can't stop. This idea does NOT explain the objection that if it was so easily defeated if you knew the key, the Forsaken wouldn't have been so wary of it that they only made six. Furthermore, the Gholam thinks to itself [TPOD: 2, Unweaving, 84] that "it had never encountered anything that could harm it" until it met the medallion. In all of its existence it never encountered a common metal like silver? Unlikely.
In KOD it's discovered that Shadowspawn can't survive passing through a Gateway. It kills them instantly. Assuming that a Gholam doesn't unravel the weave by touching it, presumably you could destroy one by forcing it to pass through a Gateway. But we have no reason to believe a Gateway wouldn't unravel just like every other weave does in the presence of a Gholam. [KOD 19: Vows]
Many. Here are some of the more popular ideas for how to get rid of a Gholam: