Hi Jasmine, interesting theories. I'm not sure they count as conspiracies until a group of people believe them to be secret knowledge of some sort.
[if you click Edit on your original post, you can amend the spelling in the title]

Tash is not a statue come to life, but an actual evil spiritual being who was worshipped as a god by the Calormenes. With his many arms and birdlike appearance, he resembles gods still honoured in some countries today.
Tash is not to be seen as an equal to Aslan, or as a version of Satan (who is also not the equal of our God/Jesus Christ).

There is nothing in the books to suggest he was involved with the people of Charn who, after all, lived in a different world (entered via the Wood Between the Worlds, not by travelling across land or sea).  Nor did Tash have anything to do with either the White Witch Jadis, or the Lady of the Green Kirtle. Not every character in a book or series will be connected every other one!

Shift and Rishda - it's hard to know when the balance of power went to Rishda, but he is definitely superior to Shift, and seized his petty little kingdom. Shift's interests were mostly getting good food and conditions for himself, and it was easy for Rishda to take over - he was a smart man and I don't believe he would have needed earlier contact with Shift, but just seized the opportunity.

Miraz  - yes, it is very common that the second son is next heir until the first son has his own child. History is full of it.
 

@coracle The argument could made as well.

With Shift and Rishda, as you've mentioned, Shift only cared about oranges and bananas (possibly to make into a smoothie ). I think after Shift got into drinking, he lost control over Narnia, so it would have made easier for Rishda to take over.

I wonder that since Jewel mentioned in the book-

"Doubtless he (Shift) has been long in secret traffic with The Tisroc, and as soon as he had found the lion-skin he sent him word to make ready his navy for the taking of Cair Paravel and all Narnia"

So it may have been a possibility that Rishda was in communication as well. Possibly after the Tisroc got word from Shift to make ready the Calormene navy (which I'm sure could be talked about in another thread), the Tisroc put Rishda in charge.

And yes, throughout history, the second son has been first line to the throne until the first son his own child...and it sure has a way to repeat itself.

Posted by: @coracle

Miraz  - yes, it is very common that the second son is next heir until the first son has his own child. History is full of it.
 

I think Miraz took it a step further by also doing the same thing to Caspian. For example, Caspian was the heir until Miraz had a son. Then Caspian was no longer the heir to the throne, as Miraz was no longer heir when Caspian lX had a son. Maybe he didn't do it on purpose, but since we're talking about theories...  

@kingedthejust That's true. I actually didn't think about Miraz taking a step further. Doesn't seem that all the villains in Narnia have the same motives? Wonder what the theories are on the power that the villains sought after.

@jasminetarkheena 

Generally, in Narnia, and likewise in most books and movies, Villains are after the throne or ultimate power of something. Especially in Narnia, we see Jadis, LOTGK, Shift, Rishda, and Miraz are all after power, or the throne of Narnia. We also see that the throne of Narnia, after Aslan of course, are given to people who had no intention for the throne at all. 

Posted by: @jasminetarkheena

Or could have been some other world that's even older than Charn? Has he been able to travel to different worlds?

I don't think as Tash as equal to Aslan, however he made quite the impact in LB. Lewis doesn't mention where Tash came from, but C.S Lewis always leaves his writing quite vague. (However I like that about his writing, it leaves you to your own imagination and theories) I do have a theory that maybe Tash came to life after Rishda and Ginger discussed in private about him. Maybe the fact that they gave him a sort of 'call' to come to life. Or it was Aslan himself, knowing that Narnia had to end at this time and allowed Tash to come and help destroy it. 

@kingedthejust Ah yes... Shift, Ginger, and Rishda have called on Tash unintentionally (though not believing in him).. saying things like, "The god Tash and Aslan and Tash and blah blah."

"It seems, then," said the Unicorn, "That there is a real Tash, after all."

"Yes," said the Dwarf. "And this fool of an Ape, who didn't believe in Tash, will get more than he bargained for! He called for Tash: Tash has come."

"Where has it—he—the Thing—gone to?" said Jill.

"North into the heart of Narnia," said Tirian. "It has come to dwell among us. They have called it and it has come."

"Ho, ho, ho!" chuckled the Dwarf, rubbing its hairy hands together. "It will be a surprise for the Ape. People shouldn't call for demons unless they really mean what they say."

"Who knows if Tash will be visible to the Ape?" said Jewel.

And were they in for a rude awakening... Ginger goes into the stable, and sees Tash in there, which causes him not to talk anymore. Shift gets hurled into the stable-

"Go and drink your own medicine, Shift!" said Tirian and hurled the Ape through into the darkness.

And Tirian takes Rishda with him to the stable, and Tash shows up-

"Thou has called me into Narnia Rishda Tarkaan. Here i am. What has thou to say?"

Wonder if Tash said the same to Shift and Ginger.  

I haven't thought of Aslan allowing Tash to help destroy Narnia.

I always got the feeling from the books that Tash was a fiction until The Last Battle, the leaders of Calormene paying lip service to his worship for reasons of legitimacy and social control. Some perhaps truly believed, like Emeth, but it was only wishful thinking on their part. Tash the deity came into being only after so many Calormenes began doing evil in his name and putting him on a level with Aslan. Their own legitimization of him truly called him into being. I think this was Lewis's way of saying evil comes from human beings (who have the power to control it) and not from some mysterious outer source. But, I could be wrong.

The gods of Charn may have been a similar fiction, or maybe they really existed and were in cahoots with Charn's rulers. I prefer the latter theory, but there's really no evidence either way.

I think Miraz killed Caspian because Miraz wanted to be king, plain and simple. I don't think Prince Caspian ever says if Miraz was the younger or the older brother, however. I always thought he was the older one. Perhaps he was a b*****d of Caspian VIII but considered the heir because there were no other children until Caspian IX came along.

@cobalt-jade I don't think CS Lewis ever specified that. Though I always had the impression that Miraz was the younger brother. I wouldn't be surprised that Caspian IX and Miraz got into arguments when they were boys.

Some of these theories are thought provoking.

Who knows when balance of power fell to Rishda in The Last Battle? I think it's likely when Shift has taken to drinking, making him lose control over Narnia. It would make it easier for Rishda to take over. He uses brains and brute strength to get what he wants, though I am inclined to the theory that he and Shift were in secret communication with one another even before the Calormenes came into Narnia. Jewel even mentions in the book that Shift " was in secret traffic with the Tisroc", so I would think that Rishda was in part of the communication as well.

With the "Into the Wardrobe" on YouTube, I think he even said that it's possible that Jadis allowed herself to be possessed by Tash. Not only that, but when Aslan tells Digory that he brought evil into Narnia, He may have been referring to Tash. I also kind of I have a theory that both the White Witch and the Lady of the Green Kirtle made a deal with Tash for their dark powers, and desire to take over Narnia.

Please note: 'Into The Wardrobe' on You Tube is not connected to the well-established C.S.Lewis website of the same name, which has been on the Internet since 1994.   https://cslewis.drzeus.net/  

The You Tube channel is creative and full of interesting ideas - but it does not have any official status,and any ideas you find on it need to be compared with the actual texts as well as the very helpful books published in the last few decades.

I was just thinking of the Dark Island in Voyage of the Dawn Treader, if it was just there randomly or could something have been behind it.

@jasmine_tarkheena 

One at least wonders why Aslan created the Dark Island. Most of Narnia is pleasant and beautiful and sometimes it is hard to understand why Aslan created such a nightmarish place. He created Calormen too, which is often described negatively when compared to Narnia and Archenland.  If you were a tourist in Narnia you might want to skip Calormen, but then again people reach Narnia in other ways than with a travel agent. 🙂

@narnian78 

I would explore Calormen because I am an adventurous person. Though if I was a princess of Narnia or Archenland, I would probably attract attention from Calormene princes or Tarkaans.

It could have been Tash behind the Dark Island. When Tash is slowly coming into Narnia in The Last Battle, it's all dark.

Another possible theory is that Tash may have been once a star in the sky that had fallen. He was probably very beautiful at that point, but somehow decided he would demand worship and rebelled. He may have been cast out of the sky and was transformed into the monstrous creature. The monstrous creature may have been a reflection of his corruption.

So possibly, Tash may have been a star in the Narnian sky, and at one point, corrupted himself and was cast out by either Aslan or the Great Emperor over the Sea.