Why didn't Ruin use Inquisitors to look for his atium?

[Ashween]

Why didn't Ruin just use the steel inquisitors to look for the atium? He relied on Vin to look for the Atium for him. Yet he was never sure if she was leading him in the right direction. Marsh showed up in Fedrax when Vin assumed Yomen had the stash. He then followed her to Lutherdel in the same hope.

Wouldn't it make more sense to just send his inquisitors to look for the cache? He was aware of the storage caverns, at least about the one in Lutherdel. Marsh showing up to stop Sazed at the entrance of the storage cavern proves that at the end of WoA. 

Marsh has also proved that he can read things written in metal when he intercepts Spook's message in HoA. So Marsh could have just read the metal plates TLR left behind and followed the clues to the next city on so on. He could have accessed the caverns more easily then Vin. Ruin would have been more certain also find out if TLR had set any traps for him or clues to defeat him.  

 

Your thoughts??

[Nathrangking]

Even if he did he would have no way of actually knowing where to send them. In letting vin and elend do the work for him all he would have to do is send an inquisitor in to seize it once it was found,

[Weltall]

Welcome to the Shard!

This is one of those things that Brandon has addressed in the annotations, so if you don't know about those you can find them on his website and they contain tons of interesting comments on the writing process, behind the scenes notes and details that we can infer but which didn't get spelled out on-page, plus some things we'd never have guessed had he not told us. Here's one comment on the caches specifically:

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In the first draft, the major draw of the final cache was the hope that it contained atium. But I realized that atium just wasn't that useful anymore—or, at least, many of the reasons it might have been useful are no longer important to the characters. Vin's instinct is right—the atium is more important than it might seem at first, but the original draft made it look like they were chasing a hope for something that wasn't even very useful. So, during revisions, I inserted Elend's acknowledgment that they don't really need atium, and I also added Vin's instinct that it's vital. We'll see how this plays out.

Of course, the reason Vin has an instinct that atium is vital is because of Ruin's touch on her emotions, driving her to seek out the final cache, where Ruin himself hopes to find that atium. To him, Vin and Elend are just another pair of pawns—in some ways more useful than Inquisitors because they don't even know they're following his goals. Ruin isn't sure if these caches will have the atium—he's in fact rather suspicious that this is a ruse of the Lord Ruler—but he's willing to dedicate some resources to the possibility, hence what he did to send Elend and Vin searching out the caches. He worries that there will be some kind of guard set at the final cache or the atium that has been told to watch for Inquisitors and keep them away, and he feels that using Vin and Elend is both more clever and potentially more effective than just sending an Inquisitor.

 

[Oversleep]

It was explained in the book itself. Chapter 64 epigraph:

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One might notice that Ruin did not send his Inquisitors to Fadrex until after Yomen had—apparently—confirmed that the atium was there in the city. Why not send them as soon as the final cache was located? Where were his minions in all of this?

One must realize that, in Ruin's mind, all men were his minions, particularly those whom he could manipulate directly. He didn't send an Inquisitor because they were busy doing other tasks. Instead, he sent someone who—in his mind—was exactly the same thing as an Inquisitor.

He tried to spike Yomen, failed, and by that time, Elend's army had arrived. So, he used a different pawn to investigate the cache for him and discover if the atium really was there or not. He didn't commit too many resources to the city at first, fearing a deception on the Lord Ruler's part. Like him, I still wonder if the caches were, in part, intended for just that purpose—to distract Ruin and keep him occupied.

[The One Who Connects]

14 hours ago, Ashween said:

Marsh has also proved that he can read things written in metal when he intercepts Spook's message in HoA. So Marsh could have just read the metal plates TLR left behind and followed the clues to the next city on so on.

What metal plates?

Marsh may be able to read them, but the caverns(and cities) are built around metal rich areas, which prevents Ruin from easily seeing them.  He may have known such a cache exists, but how was Ruin to know the difference between a metal plate with writing, the metal cans, and the surrounding metals? Ruin's tunnel vision has betrayed him more than once, so him overlooking a supply cache as simply supplies isn't too unreasonable.