Unknown Titan

The First Soul; The Elder is one of the Grave Ruins secret Colossal Titans you'll come across in Titan Souls. In the soundtrack, the song that plays in this area is called "Titan Elder".

Tips for Beating
This Titan does not actually fight you, but talks to you. You'll just need to find him, climb up the vines to reach the top of his head and shoot his weakness once to defeat him.

SPOILERS
Dialog 1:

"Ahh..."

"Another broken Soul seeking Truth"

"Less encumbered than the last..."

"You have paid a high toll indeed"

"For the abomination in your quiver"

"And for what... Knowledge? Power?"

"I hope it was worth it..."

"Do what you must."

Dialog 2:

"I was the first Life"

"The first Soul born from Truth"

"And from I, came the first of you"

"And now we come full circle"

"The maker is un-made"

"And one day, you will fall to the same fate"

"Do what you must."

Dialog 3:

"You found what you sought..."

"You killed the second God"

"The one who took my place"

"And created the Four Guardians"

"The rest of Guardians here"

"Grew from Lost Souls"

"Some were like you... human"

"They lacked your conviction for killing..."