I'll preface this by saying that it's all outside of story leaks, which I really dislike because they ruin the theories and speculation experience.

I've read a lot around talking about the entity seen in the trailers and the 'Lady Crownless' being two separate entities. The trailer starts with this sentence 'One of the Threnodians will soon be reawakened...' and on the background there's this entity

First Entity Screen

Well, the connection they want us to make seems simple doesn't it? This entity is the Threnodian that the Fractsidus want so badly to reawaken. Which would make a lot of sense, and now I will illustrate why. During the trailer we also see this image where the 'Lady Crownless', as many are calling her, appears.

Lady Crown

However, the entity has a crown. She cannot be Crownless. And from here it's just as easy to come to the conclusion that the two entities are distinct, that we are talking about two separate things.

But Kuro Games did their work well and at the end of the whole showcase, at the time of the greetings, they show us three frames that are very important in connecting the two entities instead.

Back Side

While Turning

Face Side

It is the same entity that has been deliberately placed in a position in order to hide its crown and we can see this in the next two frames when it turns towards the viewer.

Having now reached this result, i.e. that the entity seen at the beginning of the trailer, and during, is in fact the same, are we going to reason with the so-called 'Occam's Razor' and say that it is the Threnodian or that Kuro Games is trying to lead us astray and that it is in fact something else entirely?

Before answering that question, let's see what else we have. The most important event is definitely the moment when we confront the Crownless during the first part of the main story. Immediately after defeating it, Rover manages to absorb it with his bare hands and in the next instant has a vision of the same entity of this post

Rover's Vision

You can also see the crown.

But who, or what, is a Crownless?

From Developer’s Notes - The Crownless is a high rank Tacet Discord which mimics the form and actions that of a knight engaged in a ceaseless crusade. - [We know that the abilities, forms and behaviour of Tacet Discord vary due to differences in frequency information and, most often, through imitation of humans.] - Despite its fabricated appearance, the Crownless knows nothing of a knight's duty, nor does it possess any chivalry. It attempts to understand and learn the behavior of a human knight in ward of its overlord, yet fails to grasp the true meaning of guardianship the role entails.

The crown represents a child's rite of passage into adulthood, and it is also the Crownless' initial stage of imitating human beings. However, perhaps only when the Crownless truly understands the nature of human beings, can it find its own "crown" rather than merely imitate.

Although we should not give too much credit to the discontinued history of CBT1, from the latter we know that it is stated that the Crownless is a fragment of its true strength, and that its power used to be scattered to several Tacet Discord Elite around the world. Also from the discontinued story, we know that Scar was happy that Rover absorbed all the fragments so that the Crownless could be completely reborn through them.

Although the story of CBT1 is to be taken with a grain of salt, we can infer how it is also in line with the story present in CBT2, as Scar tries in every way, through the story of the Black Lamb, to bring Rover himself to the side of the Fractsidus.