"Yes." With Leareth's help, and the advice of a lot of other competent people, but he doesn't think Fëanáro needs an answer any more nuanced than 'yes'.

"That's good. I want to have a test version of the thing that will make you less tired in a few weeks. You can bother me before that if it's important." And he leaves.

And Leareth goes back to his own research. His first priority is access to Velgarth, but the current work there is magically intense – he needs to set up an extremely well-shielded workroom, and a lot of safeguards, so that he can muck around with the Abyssal Plane and try to find where the next plane is on the other 'side' of it. Everything is in a different 'orientation' than he expects, it's awfully inconvenient, but it should still go faster from here. 

When he's hit his limits with that, he can spend the rest of his time working out new artifact designs. He makes new, more sophisticated, ward-stones against magical attacks for the main camp in Endorë, since that Maia did get a good look at the old ones. He makes a shield-talisman for himself that blocks Thoughtsensing, just in case he manages to drain himself to exhaustion again and has all his thoughts 'public'. And then, after some consideration, starts trying to design a similar one that will work for Maitimo, who can't interact with it directly using mage-gift; he'll need something that's straightforwardly permeable to osanwë, but not Leareth's Thoughtsensing...

The Noldor trade with the Dwarves for weapons and armor. The Dwarves can't produce hundreds of thousands of those overnight but they can do quite well if you pay them enough. It transpires that they dislike Quendi because the locals used to hunt them for sport - "you can't read them with osanwë, they thought they were animals -" and that they are friendlier towards Quendi who had nothing to do with this and are appropriately appalled about it. 

Scouts discover Yavanna's tree-people but they are not very interested in the war on Melkor, which has not yet in any way inconvenienced tree-people.  

They capture orcs to interrogate. 

Leareth finds the Elemental Plane of Air within a week.

Do the captured orcs know anything about Melkor’s operations and deployments?

The captured orcs are all sworn to hate Quendi and never help them in any way. 

Don't suppose you could fix that?

Leareth can go test whether his magic gives him a way of getting through oaths - are they the same kind of oath that the Quendi can swear? Even if he can't, he can read their minds, he doesn't really want to reveal that capability but if they do it privately behind shields and kill the orcs afterward then the official explanation could be that they tricked them or something. 

They are the same kind of oath that the Quendi can swear; they stand out, in their minds, like a rod through their heads that all the other thoughts have grown around. 

The orcs think that Leareth, not being a Quendi, is less obviously and inherently evil but still probably evil since he's working with them. 

What happens if he puts a compulsion on one of them, to believe that Leareth is not evil and is actually on their side? 

This works fine. Maybe he has tricked the Quendi and is pretending to work for them. 

He'll imply that he's definitely done that, then, and it's very important that he find out what they know about the current deployments, which he is certainly going to use to trick the Quendi further rather than actually help them. 

Melkor sent out hundreds of thousands of orcs to go live wherever they want in Beleriand, though they will have to fight the Quendi for it. They are to take the Quendi alive, when they can, and return them to Angband, but often they cannot do that and might as well just murder them. The orcs are in small groups of between ten and fifty, though sometimes the groups will ally in order to destroy a large group all at once, and sometimes Melkor's Maiar will come out of Angband to coordinate them in a large concerted fight. One of those is planned but probably not for five years, by which time there will be ten times as many orcs and also some defenses against the evil magic the Quendi do. They don't know details about the defenses against the evil magic the Quendi do. 

Leareth thanks them for their brave assistance. 

–And then possibly these particular orcs should get murdered, because the compulsions weren't particularly thought-out to be sneaky so he oughtn't send them back in as spies until he's worked out something better, and he doesn't want them escaping by accident. Does Maitimo know if orcs come back when they die, though? That's a consideration in how much effort and risk he's willing to take on in order to not murder them right away. 

They go to Mandos but he can't fix the oaths, so there they stay. One of the things Melkor said he'd do when they freed him was help the orcs come up with an interpretation of their old oaths that let them live with everyone else. 

:I think we can fix that, someday. If we win. At worst we could find them an entire different world to live in, apart from the Quendi: And in that case Leareth is inclined to test that blood-magic works at the same time. It's not like they wouldn't have ended up killed anyway if he hadn't suggested capturing them instead. 

The Quendi have no particular taboos about blood magic and think this sounds very reasonable.

Blood-magic does work on orcs! 

...It works absurdly well, in fact, it's not ten times as much power as a human life would be but it approaches that. Leareth isn't sure how much that hints that they're more intelligent, in which case that's somewhat disturbing but then again the Quendi are clearly a lot smarter than the average human and even than he is. It seems like it might be a factor of how firmly their souls are stuck onto their bodies? He would have to do a lot of trials with annoying measurements to confirm that, though, doesn't seem worth studying it now. The important part is that if it comes to all-out war and he for some reason can't use the Silmarils, he's got a backup power source. 

Leareth is terrifying and the two major prongs of their strategic plan at this point are 1) make him more terrifying (with artifacts that deal with the endurance problem) and 2) import his friend who is ten times more terrifying. He has a complicated mix of thoughts that he's tempted to shoo away because they're not helpful but - maybe, actually, he should think them all the way before deciding that - 

- it's pretty plainly the case that Leareth could kill them all if he wanted to, which is useful insofar as it rules out that he wants to or would do it if he could. (He could probably do worse than kill them all, with the mind magic - in particular you can probably compel people to take an oath, and that's damage death can't undo and there's no ruling out that he's doing it, so this reassurance is of limited value, but - )

(there's the thing his father spoke to - that you're not much of an ally if you want your allies to be weaker, that you haven't built much of a paradise if people have to be small to fit in it -)

( - or maybe he's just rationalizing because he really likes Leareth -)

People say that orcs are better off dead. There does not actually seem to be a lot of reason to think this, watching orcs go about being orcs when not in the immediate presence of Quendi. But he doesn't really want to disabuse them of it, it might make them worse at killing orcs, and killing orcs is the bulk of their job right now. On the other hand it seems like some kind of mistake to let everyone go around being conveniently wrong.

Leareth, independently, has complicated thoughts on the question of the Quendi believing that orcs are better off dead – he thinks that with the right framework or mindset it won't make them worse at killing orcs but he isn't sure how fast he can convey that mindset or even whether he can – and he's not going to get into it unless Maitimo asks. 

Anyway, now they have numbers on the orc population, and information on their deployments and strategic objectives, and all of this is useful when it comes to helping Maitimo come up with a plan. They should start trying to take back territory sooner rather than later, before the orc population has time to grow – what's their generation time anyway, it must be absurd, especially compared with Quendi with their slow childhoods, how in all hells do you breed Orcs from Quendi and get that it makes no biological sense. Anyway. He advises Maitimo to plan offensives that reveal a minimum of their capabilities, since they shouldn't need their full capabilities in order to fight back against not-particularly-organized smallish groups of orcs. 

Leareth will be available to answer questions on that and make artifacts on request, and keep sifting through the planes of Velgarth to get to the one where humans actually live. 

(Orc questioning will reveal that time passes faster in Angband, and that orcs mostly have children once per subjective year, starting when they're fifteen or sixteen. They can have two at a time if there's reason to hurry the numbers of orcs. It has been a couple of years in Angband since Melkor returned.)

The Quendi start their offensive from three directions - the coast, the eastern mountains where the Dwarves are, the south - and kill lots and lots of orcs. 

Leareth does not at all like the part about time passing faster in Angband. It's not worth hurrying any more than they already are, though.

He finds the Elemental Plane of Fire a few days later. 

And Fëanáro works out a test version of the endurance artifact! It's a delicate silver chain with a dozen different gemstones hanging from it at even intervals. "I'm sorry it's so ugly," he says when he hands it over for Leareth to try. "It's much faster to write to and I could get other people to do the gem segments."

Leareth doesn't find it especially ugly but he doesn't say anything about it. "I understand. Thank you." He tries it on; he can test out how much it helps with endurance by running tests on accessing the Elemental Plane of Fire in his well-shielded work room, see if he can manage it longer than the usual hour or two before he needs a break. 

He has a particularly good day but not an unprecedented one.

It does seem to consistently let him have particularly good days, though.

That's pretty worthwhile in itself and maybe the next version will be better. 

He keeps working. It takes a month, with progress in fits and starts, before he finds the material plane.

Improvising his magic to wind through all the way there is exhausting. He passes a very brief message using one of his standard communication-spells, just to tell his commanders that he has news and to await further instruction. Then he'll work on a specialized communications spell and an artifact for it.