Managed to figure out what it was checking and technically abide by all of that while evildoing.

It wasn't checking for "assassinating people"?

That was the first notice they got that he'd stopped cooperating, and he fled the continent immediately!

It is customary to, when supervising someone who may do bad things, make it actually difficult for them to do them and actually difficult for them to leave custody, or at least have some way of verifying that they really don't mean to over some period of time. Addy, for example, has her mind read kind of a lot to make sure she's not up to anything.

They thought they had those. They underestimated the Enemy. He had a means of faking some oaths he made.

How'd he do that?

They aren't sure! 

Well, they're the same sort of thing, right, how would they do that if they wanted to?

They wouldn't want to, and so can't think how they would.

That seems like a drawback. Do they always have this problem? Is that why incarnates are so confusing?

Yes. To do something and to think about doing it and to desire to do it are all the same for them. Incarnates are different, apparently.

Yep. Well, what did it look like when he delivered the oaths?

They show her the memory; Melkor kneeling before them, sobbing, pleading for another chance at life, promising never to harm even the smallest creature in Arda, promising to fix everything he'd done wrong with orcs, promising to heal Arda together with them...

Well, was he definitely speaking aloud? It does have to involve speaking aloud if she remembers right.

He was speaking aloud.

Well, if vampires did oaths one could fool Elspeth by going out of her pitch range, but presumably Valar all hear the same pitches and stuff...

Depends on how they're doing their senses, actually.

How were they doing their senses?

Fourteen different answers. Some of them had incarnate forms, some of them were just aware of all things in the relevant radius but in a way difficult to translate to senses.

Well. Are the latter group sure he wasn't sneaking anything into all that sobbing?

....no.

That might be it then.

Elspeth is so helpful! Can she explain why not all the Elves wanted to come to Valinor.

Not even all the Valar thought that was a good idea, right? How was the idea presented?

They showed up and told the Elves how nice Valinor was! And safe!