"Hmm." Vanyel glances at Mahdi again. 

He is thinking that the obvious next question is what's the eventual plan that involves invading somewhere, but this isn't his destined enemy, Vanyel can do this at his own pace. (They almost definitely could stop Leareth escaping; even presuming he can hijack Mahdi and Teleport them both to Absalom and run from there, the crystal ball makes him easy to track. And Mahdi has a vanishingly small chance of missing that save anyway, forewarned and with Protection from Evil up...)

"Problems or countermeasures he anticipates back in your world from his kidnapping?" he asks Vanyel quietly.

Right, good idea. Vanyel asks. 

"I think my organization will be very alarmed, but they are not likely to blame Valdemar, since this was manifestly impossible with Velgarth magic. Several of my colleagues know of your earlier claims to me, and - I am not sure how they will update on this, and it partly depends on whether the wards could detect the magic of the portal - it looked very magical to me but mage-sight and Velgarth wards may have different detection thresholds. I think they will conclude that this was likely to be your doing, and that almost certainly you are in fact in another world, as you said, and now I am there too. Nayoki will continue researching the spell we began, and may make faster progress since she has a greater number of handles on how to target a search on me versus on you. I still expect it would take her months." 

That's all an answer to the question, and the Truth Spell doesn't demand any more, but he goes on anyway. "If you would allow me to communicate with them, I would appreciate that - or, if you consider that too risky, I would also accept you passing a message by some other route, though they would place less credence it was truly from me and un-coerced, in that case."  

It'd be easy enough to allow, if they want to, though harder to make sure he wasn't issuing orders for war. Mahdi has sufficiently little context on the situation in Velgarth that he's inclined to defer to Vanyel, here, Vanyel seems to have a good head on his shoulders. Fazil is obliged to watch this whole mess and figure out what Abadar wants and Hagan is going to end up hung up on some inscrutable Hagan thing but Mahdi figures that Vanyel will probably get things right and mostly needs people to bounce ideas off. 

He is concerned he'll forget some of these details so he starts taking notes.

Vanyel nods. "We'll consider it. If we do let you speak with someone directly, do you promise that you won't use it to tell them to go to war with Valdemar while I'm away?" 

"I swear to you, I will not." 

The Truth Spell halo doesn't flicker. 

"Do you see any of your intentions that you just expressed changing?" Vanyel asks, neutrally. 

"No. Or, very unlikely, it would take..." Another twitch at a smile. "A betrayal from you, I think, if you proved not to be who I had thought. Or a betrayal from your friends, I suppose. If you try to kill me, I make no promises about my reactions then." 

"I'm not going to hurt you, Leareth." Vanyel stops, frowns. "Er, hmm... Conditioning on everything you said being true and remaining true. Sounds like that's true for both of us, on both sides." 

He takes a deep breath. "What's your plan. That you wanted to invade Valdemar for." 

Aaaaaah this is the first question he doesn't want to answer - not because he doesn't want Vanyel to know ever, but because it's too soon, he doesn't think he's explained enough of the prerequisite concepts for it to make sense to Vanyel why he thinks this is necessary - he's not sure they'll even be able to talk about it afterward - and he doesn't have a lot of time to consider his answer, there are mental moves he can make to route around giving a full and complete answer, but the Truth Spell is already tugging him, and he thinks Vanyel will just keep pressing anyway– 

–and right now Vanyel has nearly absolute power over him– 

"I wish to create a new god," he says. "With values that more accord with mine - with ours, I am fairly sure. A god who prioritizes the flourishing of all sentient beings, and does not step on all attempts to advance civilization. This is a risky and costly plan, I am aware of that, but - I have tried all of the safer and more normal routes, and I am blocked at every turn." 

He can't tell what Vanyel is thinking, of course, but he's curious what the stranger is. 

Right, their world still has prophecy and doesn't have ascension - or at least not by a route as straightforward as the one here in Golarion - 

- hmm. It's not that it's not good for there to be more Good gods, it probably is, but it seems like the effect size is mostly pretty small. The differences in the balance of power when new gods have ascended haven't been very noticeable. People argue about whether the shifts in the balance of power are really there at all. Aroden's death was disastrous for the world but it seems like most of that was the resources expended and alliances made in the moment the gods went to war, not the absence of Aroden from the balance of power, at least if he had to place his guess. He would add a new Good god if it were straightforward, but not if it involved conquering countries - which is the sort of thing that also changes the balance of power, and mostly for Evil -

Leareth doesn't want to give away that he's reading the man's thoughts, and he keeps his eyes fixed on Vanyel.

"I have spent many centuries working on this plan, and the reasoning behind why I think it will help, when there are already many existing gods. I have also tried very hard to find an alternate power source, and failed in Velgarth, but the discovery of another world calls for returning to the drawing board, and I am hopeful. So my previous plans perhaps are not relevant anymore. My plan had been to - kill a vast number of people for blood-magic. In the vicinity of ten million. A cooperative god could bring them back, afterward, with a less lossy method than standard reincarnation. It is of course still an appalling plan and I would prefer to use any alternative I can." 

Vanyel finds himself frozen, unable to answer. 

Yfandes, on the surface, has been riding along in Vanyel's mind, and relaying the conversation, a little blurrily, to the others. She nearly flinched out of rapport at the first mention of the god, but hung on. 

:Vanyel: she sends. :This is - horrifying - we can't - he's a monster - we have to stop this–: She's gone rigid, every muscle tight and bunched. :We should maybe just push him back in there and kill him: 

:...WHAT?: Vanyel physically takes a step back, recoiling, but not from Leareth. :'Fandes, I don't - why... He just said under Truth Spell that he wants to try to cooperate!: 

:You can't negotiate with a madman: Her mindvoice has gone very cold. 

- when Vanyel flinches he puts up a Wall of Force between Leareth and them and then detects magic, trying to figure out what happened - "Van, what -"

Leareth lifts both hands, palms open. "I did not do anything, I swear." The Truth Spell is still active, the blue light visible to Mahdi as well, and it doesn't falter. 

"Wasn't him." It's hard to speak. And he's not sure he can whisper quietly enough to avoid Leareth overhearing. He shoves through an effortful Mindspeech link instead. :Yfandes is - upset - can't figure out why... Do YOU think we should murder him for what he just said? Am I the crazy one here, that I - don't think that...: 

I mean we shouldn't let him kill ten million people but there are probably other ways to ascend someone, if it's actually a good idea, and if we can't work with him the plan was to send him to Nirvana, where I think he'll fit in fine actually even if he's very badly wrong -

:That was what I thought: Vanyel keeps his expression as perfectly level as he can. :'Fandes, we're not going to let him do it. But he just said he doesn't even want to. Hellfires, maybe we can talk him into not making a god at all - this world has lots of gods, and other powerful magic, maybe he can solve the problems in our world that way. He's not wrong about the problems. Right?: 

:What?: 

:I can't believe you're even considering helping him: