I'm sure there's tons of theories on this subject, so bear with me. From what I've read on this site and elsewhere, there are a few main ideas as to what The Great Lord meant when he said "LET THE LORD OF CHAOS RULE": 1. The Lord of Chaos is Rand. Basically, just let Rand run wild and cause chaos on his own. To me, this doesn't make sense, because Rand is doing everything in his power to create peace (however momentarily), and the Forsaken are working against it. 2. The Lord of Chaos is Moridin Again, this doesn't make sense to me for a few reasons. A. The DO first gave the command to Demandred, after offering him the title of Naeblis. Why would he command a potential Naeblis to let someone else rule? B. Mazrim Taim uses the saying in a way that really has nothing at all to do with Moridin. There will be more on this later. 3. The Lord of Chaos is "whatever Forsaken causes the most unrest". Basically with this side, Naeblis goes to whichever Forsaken causes Chaos. By that logic, Rahvin, Graendal, and Semirhage would be good candidates, not Moridin. All Moridin did was help Rand kill a few Forsaken. The former three caused unrest across Randland. So yeah. I think it's none of those. My theory is that the "Lord of Chaos" isn't a literal person at all. Rather, "Let the Lord of Chaos Rule" is something of a military strategy for the Dark. To help explain what I mean, I'll give the example of Taim. When Taim is confronted with Egwene's Aes Sedai (with blessings from the Lord Dragon), he tells them they can't bond anyone before Elaida's Aes Sedai, and that they can only bond Dedicated. This forces two warring factions to sit in the Black Tower, an Aes Sedai nightmare. All the while they get to see their Sisters forced into servitude by Taim's Ashaman. It's only a matter of time before the situation blows up. And what does Taim have to say about this? "Let the Lord of Chaos Rule". Taim actually had four responses. 1. Kill all the Aes Sedai. 2. Send the Aes Sedai packing without Warders. 3. Get the whole ordeal over with, let Ashaman get bonded, and send the Aes Sedai home. 4. Postpone the whole thing, building tensions. Number 1 is a pretty bad idea. Rand would probably be pissed, which would end Taim's game in the BT. Number 2 is kinda neutral. Sure, the White Tower(s) get kinda fed-up with the Ashaman, but that just turns Aes Sedai further against Ashaman. Number 3 is downright peaceable. Number 4, while not directly causing Chaos, is almost sure to drive the Aes Sedai up the wall. It has the largest impact against peace in Randland without turning the fury of the Dragon Reborn or the White Tower(s) against Taim. That may be a bit long-winded an example, but I hope you see the point. In this situation, the point of "Let the Lord of Chaos Rule" isn't to build up the leadership of a specific person, but rather to allow or even encourage unrest across Randland. This matches pretty well with what the other Forsaken did: starting wars, pushing wars, splitting White Towers, dividing countries, scattering black-eyed Aiel, etc. So yeah. There's no such person as the Lord of Chaos.