If nobody has other precautionary ideas she'll head to a likely uninhabited-in-her-era bit of Endorë, while looking through Mairon's eyes, and see if the mana expenditure falls.

(Leareth wants a time interval after which they should assume something has gone terribly wrong, but other than that thinks this is a reasonable number of precautions for the task at hand.) 

She doesn't think it should take her more than thirty seconds.

Quick is good, less chance for anyone to find her even if her presence is detected. He waits. 

The mana expenditure falls.

She comes back. "It looks like he is in fact just sitting in a tree in my Valinor looking at the scenery."

Leareth is a some more reassured. 

:I think we ought be somewhat concerned that he now knows of the existence of other Ardas, since the Valar do, and that he will try to find this one and perhaps aid Melkor in the war. Probably the best thing to be done, here, is to remain on guard. Oh, and one good thing is that this Sauron will know very little about Velgarth magic, even if he has arcane magic, so he almost certainly cannot cancel it: Yet. 

That might not be a safe assumption, if it's similar to canceling arcane magic, but hopefully.

:I wish there were a way to test if it is similar! ...I suppose the other Valar here can also cancel Velgarth magic, since they blocked Gating, but given their track record I am not very eager to involve them in our research or strategy planning. Also the fact that there are gods, but it is possible I am unfairly prejudiced against gods due to the Velgarth ones specifically being the way they are: 

Without even a little help from at least one Vala I'm not sure how to safely get Mairon Voided. I can only summon him to me, not to a different place; once he was physically nearby he'd have a short window before Olórin could do anything or I could teleport out. Maybe we could ask an Aulë if there's anything he could do without being there himself to also get Voided; Mairon ostensibly works for Aulë, who also voted against banishing me.

:How much modification work to the spell would it take in order to instead teleport him to a different place?: 

Uh... some. It's not necessarily intractable but it would take at least a couple of weeks and maybe more.

I guess I could bring in my Olórin if he's up for it, since he knows wizardry already, and teach him the spell and give him the Voiding-thing.

:Right, and then he could cast the teleport spell himself to summon the other Sauron, and then immediately trigger the weapon, while also being less vulnerable than you since he is a Maia too? It does seem worth asking: 

Yeah. Is the weapon in fact reusable or does this also require a trip to my Velgarth to get another one?

:I will have to ask Vanyel; I do not know anything about it: 

I'll start summarizing to my Olórin while he wakes up the rest of the way.

She sighs and explains the situation to her Olórin.

Wow. Well, if the Valar had possessed any common sense at all, then this situation would never have arisen, so they cannot be too grieved we decided to solve it without them. I will do that, if you think it will help.

There might be a better idea but I'm a little worried we need to be quick, even if right now all he's appearing to do is sit in a tree he might have figured out how to do research in his head or have an earcuff like mine he's talking to who knows who with.

That makes sense. Right now is not a particularly bad time for me.

Okay. I'll let you know when we're ready on this end.

Leareth talks to Vanyel, who's fully awake now though still very low on reserves, and ends up carrying him out to look at the weapon (now on the ground with a wide perimeter marked around it, and wards, so the Noldor troops stay clear).

:We are fairly sure it is one time use: he tells Bella. :I suppose you need make a trip to our Velgarth for a duplicate. We probably should not wait until Vanyel is rested enough to Gate, and I am not sure he feels like giving me the ability to Gate to a number of superweapons, although I am definitely not going to steal them. He could perhaps share his memory of the place with you, if that would be sufficient for the teleport? He also had a shielded bag for transporting it, although he reports that the weapon was stable and there should not have been any problem even if it were unshielded: 

The memory should do, and I might as well take the bag.

Vanyel can share the memory of the right weapon room in Urtho's Tower, and have the discarded bag brought to her. :Be careful: he tells her. 

Does that advice have any more specific content?

:It would if you were a Velgarth mage! I have no idea what sort of magical senses you have, if any. Get out right away if anything weird happens? The weapon shouldn't even be possible to activate without a Maia helping, since Olórin's part here was being the core and energy-channel, the design is incomplete. It's the only weapon in that room; if it looks different than the cube-maze, you got the wrong room somehow, don't take a weapon unless it's identical. I visited the one in my world later, but I can't see how fifteen years earlier could have any other hazards, the place has been buried for eighteen hundred years: