Hmm. The tale of the Forbidden Ones is interesting. I'm assuming the Time of the People's greatest need" was during the war with the Titans? So, maybe the Forbidden Ones shed their form and returned to a spirit world because they could see that the Evanuris were Falling. As in becoming increasingly intoxicated by the heady brew that is corporeal existence. And succumbing more and more to these powerful sensations.
Solas talks about how current Thedas is like walking amongst the Tranquil--ofc meaning that their connection to the Fade is severed for the most part. Yet, I feel the term tranquil would suit the spirits better because they're the ones that live in this static state of being. One note. One tone. It is not until they brush up against the corporeal world and its inhabitants that they come to know pure, uncut emotion; and it overwhelms them. Much like the way Cass describes when a Tranquil "wakes up". She says they lose all control of their emotions. They become erratic and cannot focus. It's overwhelming.
I wonder this because reading a codex from the Dead Hand puzzle place, it shares the story of how Falon'Din became the guide of the dead. He and Dirthamen are just skipping around, smelling the flowers, listening to the trees, helping old dying deer and all that. They never knew sorrow at that time. It was all bliss.
What changed? We can tell from this codex that it was from early days of Evanuris because Falon'Din was just becoming the Dead Guide. All I can think is that the allure of corporeal experience eventually entangled them. Or could they're time in Form have slowly started to disrupt their finely tuned connection with the Fade (like Cole), and so they looked for something else to aid them--lyrium. And felt they needed all that lyrium in order to regain that level of power.
I also wonder about this codex: The Raising of Sonallium--(pulled from DA Wikia):
"The pages of this book—memory?—describe a heated argument between a group of well-dressed elves inside an elaborately arched pavilion on an island floating in a void. In the distance, haloed by a blizzard of light, thousands of elves are maintaining an elaborate magical ritual that pulls raw essence from the Fade, funneled into a sphere in the air. Through the lens of the sphere can be seen a world of indigo waterfalls and rust-red jungles, and a temple palace so frescoed and cleverly carved, it is a masterpiece in itself.
The well-dressed elves' shouting grows so loud, it can be heard over the magic. One leaps at another, howling and pulling out a knife burning with prismatic flame.
"Architects of the Grand Sonallium (a gift from Blessed Sylaise to Clever June as thanks for a great favor) in friendly debate over the color of the palace's roof trim."
Besides the fact that these people were leaping at each other--howling! and trying to shank each other with burning prismatic blades, I'm wondering what world they're observing? The one with the rust red jungles and indigo waterfalls? And are they able to go through this sphere in order to decorate the roof trim? Or...what's happening here?