Brightstar is unsurprised to be dead. He's not especially upset, either. 

He follows Strange. :Did we get Thanos too?: he asks. 

"I don't know. Probably not. He was farther away from the explosion, and he's a lot stronger than we are even without the Stones."

They find Mandos fairly quickly.

WHO ARE YOU? he asks.

"Uh, I'm Dr. Stephen Strange. You probably don't know me yet, I died while time traveling, but future you sent me back once already so do you mind doing it again?"

ONE OF MORTAL RACE HAS RETURNED TO LIFE BUT ONCE BEFORE, AND FOR A PURPOSE OF DOOM INTENDED BY THE ALLFATHER HIMSELF. WHO ARE YOU, THAT I SHOULD GRANT YOU THE FATE OF BEREN ERCHAMION, FOREFATHER OF THE KINGS OF MEN?

Brightstar has no idea who Beren Erchamion is, or what's going on here in general, and he doesn't currently see why he should care. 

He takes a step forward. Glares at the strange figure of Death. 

:Where are my parents: 

He looks closely at Brightstar.

VANYEL ASHKEVRON AND SNOWLIGHT K'TREVA ARE ALIVE. AS ARE—

He pauses. That can't be possible.

As are you.

"Yeah, I told you, we're from the future. Where a maniac has killed half of everyone, including you guys. We're trying to fix it, so would you please let us out of here?"

I DID NOT BELIEVE YOU AT FIRST, BUT NOW THAT I LOOK MORE CLOSELY I SEE IT. YOU DO NOT BELONG HERE. YOU VIOLATE THE HOLY DOOMS OF ERU ILLÚVATAR BY YOUR MERE PRESENCE IN THIS TIME. ALAS, I CANNOT RETURN YOU TO YOUR OWN, SO I WILL HAVE TO HOLD YOU HERE TO AWAIT THE JUDGEMENT OF MANWË, ERU'S VICEREGENT IN THIS WORLD.

Brightstar is not really processing any of this. 

:Starwind and Moondance k'Treva. They died - Thanos killed them, I need - you must have them - you have to let me - please -: 

THEY ARE NOT YOUR PARENTS, BUT THEY ARE ALSO ALIVE. THANOS HAS KILLED MANY, BUT NOT THEM. IF YOU ARE INDEED FROM THE FUTURE, WHATEVER YOU ARE THINKING OF MAY NOT HAVE HAPPENED YET, IN MY TIME.

Pause.

I HAVE TAKEN COUNSEL WITH MANWË, AND HE WILL PERMIT YOU TO BE REEMBODIED, AT LEAST TEMPORARILY, IN ORDER TO MAKE YOUR CASE BEFORE ALL THE GODS AT THE RING OF DOOM.

He skips the usual naked-in-Lórien thing, and puts them, with their usual clothes but without their time travel suits, in the middle of the Máhanaxar, then goes there himself.

The Ancient One, who does belong in this timeline, is left behind. This wasn't the end she predicted—there is so much left to do—but it is, apparently, her end nonetheless.

She walks down to the misty sea that borders the Halls, and departs this world after four hundred years in it.

Dr. Strange and Brightstar are in a grassy field, surrounded by gods seated on thrones. Ahead of them, at apparently the head of the ring, is one with white hair and blue eyes that burn with tightly controlled power. His voice is stern.

YOU STAND ACCUSED OF DISRUPTING THE FATE WHICH ERU, THE ALMIGHTY CREATOR OF THIS WORLD, HAD PLANNED FOR IT. WHAT HAVE YOU TO SAY FOR YOURSELF?

"Uh, if Eru is so almighty and doesn't want us disrupting his precious fate, he shouldn't have let us travel back in time in the first place. I know he stopped the elves from doing it, somehow."

Brightstar is probably not paying very much attention to Manwë, because next to him is a goddess with stars in her eyes.

...That doesn't make sense? Right? 

Brightstar takes a step forward despite himself. Then another. 

:You - are you - why...: 

And suddenly he's too angry to form coherent words, too angry to focus on her star-filled eyes, he's almost too angry to form thoughts - 

:Why. Why did you let them die. They were. Your. People. You - owed them - you owed us - better than, better than - that...: 

Varda is kind of confused by this random teenager who hates her for some reason.

I DON'T KNOW WHO YOU ARE, she says, AND I DON'T KNOW WHOM YOU MEAN BY 'MY PEOPLE', BUT MY MAIAR AND MY HANDMAIDENS ARE ALL DEFINITELY STILL ALIVE, AND YOU ARE DEFINITELY NOT ONE OF THEM.

I THINK YOU HAVE ME CONFUSED WITH—SOMEONE ELSE—? (But who, if there are still rogue Maiar around she wouldn't expect them to go for looking anything like her.)

Manwë considers Strange's argument.

WHY DID YOU COME FROM ANOTHER STRAND OF TIME TO DISRUPT THE FATE OF OURS?

"Uh, Thanos. Big purple bastard, wants to prevent overpopulation by wiping out half the population of the universe. Has been making progress towards it the hard way, for a while, but six years from now he gets all the Infinity Stones and does it with the snap of his fingers. He includes you guys, by the way—including you specifically, I think—so you should probably be interested in helping us fix it."

Brightstar mostly ignores Varda's words, but after a minute or so he's all out of rage and also energy. He sags to the ground, sobbing. 

It wasn't even enough. They probably didn't get Thanos. It was all for nothing. 

At least his sister got out alive. 

...All right, focus, he's - apparently not dead anymore? Though he's stranded in a different timeline and also, it looks like, not on Earth. 

Or on Velgarth, probably. None of this makes ANY SENSE. 

:...Are you not the Star-Eyed Goddess, whom the Tayledras serve in cleansing the lands?: he asks her, tiredly. 

I WOULD NOT BE SURPRISED IF I WAS CALLED THAT BY MEN SOMEWHERE, BUT I HAVE NEVER HEARD OF THE TAYLEDRAS. MY NAME IN THE TONGUE OF THEM THAT KNOW ME BEST IS VARDA ELENTÁRI.

She's been halfway listening to Strange's exchange with Manwë, and joins it now.

THAT WOULD INDEED BE CONCERNING. HOWEVER, IT SEEMS—ENTIRELY IMPOSSIBLE.

"It's not. It happened. Or, will happen, for you, I guess."

WOULD YOU PERMIT US TO EXAMINE YOUR MEMORIES TO BE SURE OF YOUR HONESTY?

"Can't say I'm thrilled by the idea, but I'm sure you could probably do that anyway if you wanted, so—yeah, it it'll help us get out of here faster."

Manwë looks at Strange's memories. The process is quite unobtrusive—Strange doesn't even notice.

IT APPEARS THAT YOU ARE TELLING THE TRUTH. HOW THIS COULD HAPPEN, WE DO NOT KNOW, BUT IT MUST BE PREVENTED FROM HAPPENING HERE.

Thanos—the 2012 version, without any Infinity Stones—appears in the center of the Máhanaxar, immobilized.