Long story short, my character traded his soul to an erinyes for a rank of high position within a faction. His soul was converted to a soul coin. I don't know much about this, but I suspect a trip to the 9 hells will probably be in order to retrieve it. Thoughts on schemes that could help him retrieve it?

You could go to hell...or try and trade the erinyes for something it would consider more valuable. Most likely another soul or souls.

I’d keep locate object handy. Just in case you get close. 

Quote from Cardinal_Fang >>

Long story short, my character traded his soul to an erinyes for a rank of high position within a faction. His soul was converted to a soul coin. I don't know much about this, but I suspect a trip to the 9 hells will probably be in order to retrieve it. Thoughts on schemes that could help him retrieve it?

 Become a Warlock and pact your soul away so tracking down the coin becomes your patron's problem, not yours.

So the first question is going to be - Are you looking for the erinyes, or are you looking for the coin?

If the erinyes has the coin, you're good to go.  I'm not even sure you need to go to the Nine Hells.  You may be able to summon that devil.  Offer them something they want even more than your soul, which it sounds like might end up in the economy sooner or later anyway.  The destruction of a hated enemy.  A chance at advancement through the ranks of Hell.  A really powerful magic item that they can use again and again to get other adventurers to sell their souls.  Cool gambits like fiddle contests might work on your DM, but the erinyes already has your soul, so you need something to bet.  You could also try threatening them.

If you have to go there and you're looking for one soul coin in all of Hell, your DM will have to work that out with you.

I know where the erinyes is; what I don't know is if the coin is with her. I do like the option of adding warlock multiclass to this character as a result of this, somehow, and am trying to figure out how and who that would be. I like the idea of "in exchange for patron finding my soul coin and returning it to me, I will vow to serve <insert patron name>". 

Maybe you can make the Erinyes or its superior your Warlock patron in exchange for getting your soul back after providing some future services?  That gives your DM a lot of potential story hooks to use for you, which might make the erinyes more likely to accept your bargain.

I'm actually leaning to pursuing this route. It'll be interesting b/c where we play is at a FLGS, and it's pretty much open to anyone who comes. We're trying to keep the sessions down to one-shots for that reason, and at times we have had as many as 14 players, so I'm going to be helping DM a table, but at the same time, I'm like "but my character's soul...." :D

Seems odd. Normally souls aren't taken and made into soul coins until the person dies. Up until then it is just a contract. 

So, you're already well into unfamiliar homebrew territory.

I guess find the coin and have some DM-created method of turning the coin back into a soul and re-inserted. Or maybe killing the Erinyes? Although if the coin has been "spent" it is no longer hers anyway? Or check the contract - maybe there's some clause or something you can use to get out of it and breaking the contract somehow returns the soul?

I dunno. This is really more "check DM" thing, since if we're in Forgotten Realms/Books territory your situation is impossible.

When in doubt, use a Wish.

GAH! "Impossible" should be my character's middle name. 

I know the DM was having to work with lore from the 3.5 days, and may have taken some liberties, but by canon to our table, my character does not have a soul. Though I thought it odd, I rolled with it. I think it's good opportunity for story telling and unique character development. 

I did negotiate for a "bedroom" opportunity with the erinyes b/c my rogue is a bit of a ladies man, and if any opportunity to possibly kill her would exist, it might be during that time, which will be super awkward to RP :D

It's definitely interesting to see how different games make use of "souls". Being a "soulless" character does seem like it would be very interested to roleplay, especially if you want to get into the nitty gritty of what that actually means and what a soul actually is.