*nods* well, I feel ya, but it is at least addressed in canon. So much more Daniel and Armand is always needed and wanted, tho! That’s what fanfic is for ;D 

@monstersinthecosmos has some good Daniel/Armand stuff on AO3 you should definitely check out.

[^X fanart by @garama,

i added captions to blank bubbles *u*]

Essays could be – and probably have been – written on the topic of Daniel’s sanity, and on his relationship with Armand before and after he’s turned. Whether it’s real insanity or a “spell” as Marius calls it in B&G, Daniel and Armand are not compatible for a period of time in canon. 

TL;DR: Daniel and Armand’s fallout is at least addressed in canon. It seems to me that Daniel left Armand of his own free will, and Marius took him in at some point. It doesn’t seem to be a secret from anyone involved. 

Hit the jump for more, cut for length.

“Also, I got a bit upset that Marius had Daniel but didn’t tell Armand until much later on the books.”

Well, that’s our unreliable narrator/retconning that AR does. Daniel is turned in QOTD and we see some of his fledgling struggling. I don’t think Daniel’s in TOBT at all, bc that’s a mostly Lestat book, as is MTD, so it’s TVA when we find out from Armand what’s happened between him and Daniel. Then we get a glimpse of Daniel living with Marius in B&G. So Marius couldn’t tell Armand about it sooner than that.

So no, they don’t get a whole book in canon, but we do see where Daniel went and we get some explanation about it.

It seems to me that Daniel left Armand of his own free will and at some point, Marius took Daniel in. Armand says in TVA:

With Benji and Sybelle I rejoined the world in a way which I had not done since my
fledgling, my one and only fledgling, Daniel Molloy, had left me.

Marius tells Thorne in B&G:

“… I took Daniel with me because he needed me. I took Daniel because it’s unendurable
to me to be utterly alone…”

And then in PL, there is a closer relationship implied between Daniel and Marius, possibly a legit canon ship.

I don’t know how much Marius was trying to protect Armand or anyone else from Daniel’s insanity. I wouldn’t necessarily label it “insanity” either, but that he was going through a difficult time. Everyone has their own headcanons about it.

Armand in TVA, he doesn’t say Daniel is insane, just that he and Daniel are out of tune:

Daniel, though alive and wandering, though civil and gentle, can no more stand my
company than I can stand his.

…

I was no Marius to him afterwards. It was too exactly as I supposed: he loathed me in
his heart for having initiated him into Living Death, for having made him in one night
both an immortal and a regular killer.

…

There was never any innocence for us, there was never any springtime. There was
never any chance, no matter how beautiful the twilight gardens in which we

wandered. Our souls were out of tune, our desires crossed and our resentments too
common and too well watered for the final flowering.

Marius explains it to Thorne in B&G, it seems more like being “under a spell,” not a loss of sanity:

“Have you ever seen one of our kind under such a spell?” Marius asked.
Thorne shook his head, No, he had not. But he understood how such a thing could
happen. 

“It occurs sometimes,” said Marius. “The blood drinker becomes enthralled. I remember
centuries ago I heard the story of a blood drinker in a Southern land whose sole passion
was for finding beautiful shells along the shore, and this she did all night long until near
morning. 

She did hunt and she did drink, but it was only to return to the shells, and once she looked
at each, she threw it aside and went on searching. No one could distract her from it.
Daniel is enthralled in the same way. He makes these small cities. 

He doesn’t want to do anything else. It’s as if the small cities have caught him. You might
say I look after him.“ 

Thorne was speechless, out of respect. He couldn’t tell whether Marius’s words affected
the blood drinker who continued to work upon his world. Thorne felt a moment of
confusion. 

Then a low genial laugh came from the youngish blood drinker. “Daniel will be this way
for a while,” said Marius, “and then his old faculties will come back to him.”

^Marius seems to be saying this is some kind of temporary spell, he doesn’t seem to be doing much in terms of mental health care for Daniel other than being supportive and taking physical care of him.