You first "see" them in the beginning of that dark chase sequence, but only as a silhouette. They make the same noise as you fully see them in the Third Sanctuary.
I assumed they were spawned from... well, a Titan. But there was no Titan at the time. So how are they already there?! Ralsei clearly knew what it was, too.
Do they actually just (or also) spawn from really dark places...?
THATS WAHT I WAS WONDERING
Yes, their description says they spawn in the dark. Ralsei gets nervous in the first dark section for this reason. The implication is that Titans themselves will eventually form from darkness.
That implies that
Light = Light World
Dark = Light World but reduced/nonexistent vision
Darker = Dark World
Yet Darker = Titan Spawn and, eventually, Titan(s)
Just based on Ralsei's explanation of things during the beginning of Chapter 3.
Then opening (a) Dark Fountain(s) in a Dark World creates enough darkness that a fully grown Titan appears.
I don't know how logical it is to say that areas of the dark world which are visually darker (lack of light) actually contain more of what the game calls darkness (anti-light coming from fountains)
This seems like it would surely be less of it
Since titans and titanspawn are manifestations of the fear of darkness (lack of light) formed from the darkness (anti-light), it's not a big deal either way
And if you: Take out the light that wasn’t there from the darkness from the light that was taken out from the darkness without the light that wasn’t there, you form a Mature Titan.
(resuming, if you open a Dark Fountain inside a Dark World, you make a Titan. What if you maked a Dark Fountain inside a Titan??)
Titan squared
If you open a dark fountain inside a Titan, it gets massively larger and the Roaring immediately starts.
Because this one is certainly fatter than the one we fight
Maybe Titans have an hierarchy?
This large Titan: King or the stronger
The Knight looking ones: Royal Guard or the offensive strength of their race
The type we fight: operators, weakest
SPAWN
Roaring Knight?
The Knight would go above the type we fight, as they literally MADE ONE.
But, no matter how strong he is, if he does not dodge such, he would be splatted 
into the ground if the Titan: Stepped on him; Punched him down; and fired one of those beams at him
an army of Titans would be cool, but for now the Roaring won’t happen :(
Gutton
Glutton.
He said what he said.
my gutting is ON
