Altair notices when Desmond quietly leaves the room and disappears. When he can't find him after a few minutes, Altair assumes Desmond must have gone back to his own time, presumably to reconnect with Ezio. Sure enough, it's not a very long time after that when Altair feels Ezio slot into place in his mind. Technically, Ezio is in Desmond's mind, not Altair's, but Desmond is in everyone's mind these days, the common point of connection between all of them, so Altair can feel when Ezio starts taking up room in his head. It's vague, more like a place where Ezio's mind could fit, if he were there.
A few minutes after that, they all feel it when Ezio dies. There's a kind of snapping feeling inside his head, like a rubber band pulled back so far that it breaks. It hurts so much that for a second Altair is left reeling from the shock of losing Ezio. The whole room goes totally quiet as everyone looks around at the others to see if they'd noticed, if they knew what it was, if it was too late to fix it.
"What just happened?" Shay demands, turning (for some reason) to Altair. In fact, they're all looking at him.
"I don't know," Altair snaps. Because he's missing Ezio, too. "I don't have the answers, I don't-"
"Ezio's dead," Edward says. Alone of all of them, he looks more angry than shocked. Then again, Altair has seen enough of Edward's life to know hitting and yelling at things is how he handles the unexpected- he'd spent his younger years as a pirate, and hitting things is a pretty effective strategy in most situations.
"Who?" Shay asks. He looks utterly confused by all this, and Altair can't blame him. The poor man's never even met Ezio, but here he is with something suddenly broken inside his head.
"Ezio," Altair says quietly. "He's- he was one of us. Now he's gone."
And the worst of it is that Altair can still feel traces of Ezio lingering inside his head. He pictures his mind as a patchwork quilt, bits and pieces of himself and Desmond and the Kenways and Shay and yes, Ezio too, But Ezio's pieces have been torn away, there are holes in his mind where his friend should be. That would be bad enough on its own, but Ezio hasn't been torn away neatly. The threads where he should be connected to Altair's mind are still there, little painful reminders of where Ezio should be, but isn't.
He might have stayed lost in his own thoughts indefinitely, except that suddenly Desmond is there, falling out of the future, red eyed and choking on sobs. Shay, who happens to be the closest, jumps to his feet and reaches out to steady him. Desmond clings to the touch, eyes vacant and chillingly empty as he hangs onto Shay like the man is the only thing tying him to solid ground. Altair can't really blame him for the reaction- by the shell shocked look on Desmond's face, Altair assumes he'd been there when Ezio died.
Without saying a word, he moves forward to rest his hand on Desmond's shoulder, squeezing slightly and waiting for his descendant to explain. He's not expecting any of the others to copy him, but suddenly they're all on their feet. Chairs scrape against the floor and quiet footsteps converge around Desmond. Hands reach out, one on an elbow, another on his head. Connor, swaying slightly from these few steps, is more leaning against Desmond than anything else.
He seems to take some kind of strength from them all standing around him, a wall blocking out everything and everyone else, and finally he takes a deep, shuddering breath and starts to speak. His story isn't exactly surprising. They already know Ezio is dead without Desmond telling them, and even the details are mostly things they could have guessed without him. But hearing him describe it in his own words is helpful, somehow. They know the worst, at least.
"He went peacefully," Altair says at last. "That's good. It's the least he deserved."
"I can still feel him," Haytham says. "Just a little."
Desmond nods. "He said he wouldn't be totally gone while we're still around to remember him," he says.
"Good," Altair says. "Let's keep remembering him."
"So what happens now?" Edward asks.
"I don't know," Desmond admits. "I went into Abstergo to find out what happened to you guys, and instead I got you all back." He manages to crack a small smile, and jerks a thumb at Shay. "Except we traded Ezio for this loser."
"Hey!" Shay protests.
"Too soon," Edward tells him, shaking his head.
"It's been a couple hundred years," Desmond says. "Technically."
"Oh come on!"
"And Ezio would be disappointed if we gave up just because he's gone," Connor says. There are nods all around, and slowly the group breaks up. Altair finds himself drifting toward Desmond, and they withdraw to have a slightly more private conversation.
"I always hated it when someone says stuff like that," Desmond whispers. There's no real reason to be quiet, but no one in the room is speaking aloud. It feels like a wake, despite the absence of any body. "Ezio doesn't get to complain about what we do or say about being dead. If he'd stuck around, he'd get a say, but…" Altair waits patiently. "He wanted to go! I couldn't stop him, and he just… one second he was there and then he was gone. Why would he leave?"
"Why does anyone leave anywhere?" Altair asks. "We have places to go, things to do. Maybe we want to see what's outside. Ezio was just… ready to see what would happen."
Desmond seems to think this over, then he nods and manages a smile that actually looks sincere. "It's just weird," he says. "Two years ago, I was in an animus watching him be born. And now he's dead, and it doesn't feel like enough time. Like…" he struggles with the words, and Altair waits patiently. He has seen a lot more death than Desmond has, and while Ezio's death hurts him as well, Desmond is clearly trying to figure out how to react. "He was just this little baby that couldn't even breathe on his own. Now he's…"
"I know," Altair says.
-/-
LONG A/N coming up. Sorry. But I did say I would explain why Ezio died if I got a bunch of angry reviews and I got eleven (technically not all of them were angry but there was still a good amount) so here goes.
To start with: this is something I've been wanting to do for a very long time. Ezio doesn't live a particularly long time after the end of Revelations, and every time I forced him into another complicated adventure instead of letting him enjoy his retirement I felt like I was going against his character. But I didn't kill him then because there was never a good opportunity.
This time, with Ezio disappearing for over twenty chapters, it seemed like a good chance to let him die. It just doesn't make sense for him to keep going at this point (so to the person that asked if I would have killed someone else if they happened to come back last- no. Ezio was last specifically because I wanted this to happen).
Other contributing factors:
-I don't really like writing Ezio (he's super difficult)
-People started leaving reviews asking if he'd died of old age, so I figured it wasn't that unreasonable
-There are now six POV characters. With Ezio there were seven, and when Arno showed up there would have been eight. That's way too many
So I really am sorry if you guys were upset by him dying. I was aiming for 'bittersweet sad' but judging by the amount of 'confused and mad' I saw in reviews, I sort of missed the mark.