What exactly means the "Lord of Chaos" instruction of the DO, it's of course an RAFO-question, but we have also a lot of hints. No doubts there's something to do with the increasing of chaos in favour of DO, but actualy there are more obvious things about it. Obvious if not for us, the readers, then for everyone WoT-Worlder from the Westlands.

DO's instruction of course is given to the Forsaken and they are not 3Age Westlanders, but the fact, that RJ places the childrens chant about the Lord of Chaos in the beginning of the LoC books, which beginns with the DO giving the command, that means, that the chant explains the DO's "Let...rule!". And what DO said to Demandred couldn't be so well known that even children from the 4Age are singing about. The chant means that everybody in WoTWorld knowed what "Let LoC rule" is (if not everyone from 4th Age, then at least everyone from the just preceeding period) So it isn't clear, what exactly DO meant, but it is NOT a riddle.

In the last chapter of BWB - that about Calender, there is a description of an annual feast, the Feast of Fools, popular in all the Westlands. In that day powerful and wise people have to obey to all commands of a fool or another low-ranked person chosen to "rule" that day. There are different names for this "ruler" in different regions, and one of them is "Lady of Chaos" (!). If an Westlander from that region would hear our "riddle" he would think it means "Let us celebrate the Feast of Fools!".

There's something in the list of the holydays in BWB about that Fool's Day - unlike the other ones it have different date in Borderlads and all other lands. I think that detail is a way for RJ to hint that there's some special about that specific feast for the series, that the reader has to pay some more attentoin to it. And the chant seems to refer to the Feast of Fools too. Most likely the "jackdaw fool" is just another word for "Lord of Chaos".

There are many real medieval and ancient european customs similar to the Fool's Day and that's something what happens in Carnival time or it's equivalents. Allways it's a day when all social and cultural roles are changing, people wear improper for their status clothings, make things that would be scandalous for them in any other day and prefere the reverse to the normal order. And all thet carnival customs have their origin in ancient rites for recycling the normal way of life, giving it a new beginning. And the original of the fool-rulers role is that of the person, which has to be sacrificed at the end of the ritual. But before he's killed for the sake of the community, in that day he has great privileges, he's "sacred king". The recycling of the life is connected with the cyclic concept of Time, common for ancient Europe.

Well, RJ builded his world by "backengeneering" all what he had readed about different real cultures and whitout any doubt he used a lot from medieval Europe. Especially there's lot of real european feasts in WoT (let begin with Bel Tain). And RJ shows us in the series plenty of wonderful Carnival scenes and huge number of Carnival assotiations. When RJ stresses something without obvious importance for the story, that's allways a clue. Therefore the carnival motive is something very important for the WoT.

Back to DO's words - There's nothing in the text that Demandred and the other Forsaken don't understand the riddle, they act like they understand, they are only surprized. When Demandred says what he's instructed to the others, he's doing it in such way, as if he's beginning some ceremony. And IIRC he's laughing while saying that. I think Demandred and the others are hearing in DO's instruction the beginning of some Carnival-like game.

And we see many Carnival-like things in the Shadow's work since LoC - the ironical reversed new bodies of Arangar and Osangar, the Myrddraal with a sense of humour (unbelieveble), stopping special operations of shadowspawn, making powerful people establish crazy rules (in WT, Shaido, Arad Doman) and ... acting for all the organizations ressemble Fool's Day with their sacred kings or queens with reputation of fools and supposed to be sacrificed later. Thats the case with Egwenes choosing for "sacred" Amerlyn in Salidar (cf Delana's support), Elaida's position after Dumai wells, the second Seanchan invasion as coming of the perfect order just to weaken the Westlands, the "faithful" to the Dragon Black Tower under Taim, the foolish Arimilla as head of the Andoran rebellion, the sacrifice of the most Forsaken at Shadar Logoth and so on. And there are lot of Carnival scenes since LoC.

And of course Rand must be too somehow in that plan, if all this is true. A problem here is, that Rand was kidnapped after DO's order, and this do not seem like letting him rule. The kidnapping operation was in process in the time of recieving of the order though, Galina's team was on the way to Cairhein, it would be tricky for it to be stopped. And maybe Mesaana hoped just to make closer the part of Feast about the sacrificing the Sacred King. But it's the only problem about Rand being a sacred king too. It's just after Dumai Wells when Demandred is reporting success to DO concerning that new orders. Everybody is attempting to use Rand's power now for his purposes, without openly confronting him (except Sammael, who didn't received the order). Morridin in his sha'rah game is now playing obviously that of the 3 variants to win, that is to force the opponent to move the fisher in Morridin's own field (the third option, we don't know what is, is something he played before and losed, and for the first option, he do not control the Fisher), and that matches in the Fool's Feast plan. The prophecy about the man dying and a fire prepared for his funeral, and also the prophecy about the three women in a boat with him, if compared with Arturian and another Celtic myths, which are sure to be used by Jordan to form Rand's character and fate, are speaking about the sacrifice of the Sacred King (aka King Arthur's death etc.). There's lot from common knowledge about carnival-like feasts, that can explain lot of details in the Dragon.

But the Carnival is not only Shadow's aim, it's the aim of the Wheel itself too. The end of an Age is the perfect thing for to be ressembled by Carnival and the Dragon's function in the Pattern is very similar to the one of the Jester-King of Chaos. The Dragon is reborn for to bring radical changes, i.e. great chaos, and that's supposed to be the hope of beginning of new recycled world - just the idea beyond the real carnivals. The Wheel Itself is celebrating Feast of Fools now.

And what DO intends giving his instructions to Demandred is beginning playing the Light's game against the Light. Before LoC the Shadow's minions ressemble sacred fools, after LoC that are puppets or renegates in that role. From the 3 ta'verens only Mat is hunted by the Shadow and Mat is The Trickster, the Light's Jester-General, i.e. an concurrent to the DO's version of the Fool's Day. DO's game is to make the Fool's Day his own Fool's Day, not the Light's one. Chaos is something needed for every change and both Light and Shadow want change. And the Fool's Day of the 3Age is the battlefield between them.