NPC: The Vendor

This post is inspired partially by Diablo 3, and its Treasure Goblins. I like the idea of an NPC that's not necessarily helpful nor antagonistic, but is purely out for its own interests. While that may describe most NPCs at first, it's sometimes very hard to actually roleplay, since PCs like to rationalize their way out of anything. But this NPC has only one thing that it's after, and that motivation drives its every action, vastly simplifying the way you actually play it out. Credit for the image to Shreya Shetty.

Name: The Vendor
Race: Demon
Alignment: Lawful Evil

Appearance:
The creature is bloated and massive. It has thick grey skin with countless folds, leading up to a face that resembles a furry spider. It has arms protruding out of it's sides, each with long slender claws or tentacles grasping at various items and coin.

Profile:
The Vendor is a demon that resembles Greed. It has an unquenchable thirst for wealth, and the procurement of valuable items. It is almost immobile, but has powerful magic alongside a slew of magical items that make it fearsome in combat. It mostly acquires wealth by making heavily lopsided deals with mortals. Whenever it finds a mortal with sufficient wealth to catch its interest, The Vendor will manifest to them and attempt to broker a deal. These deals almost always favor The Vendor. It is also open to trade, so long as the potential buyers have something that it deems valuable.
The Vendor has servants that go out and actively search for wealth. These creatures range from lesser demons to mortals, with no consistency between them. Their minds have been corrupted by greed, and The Vendor uses them to go where it can not go easily. Unlike most demon lords, The Vendor can pass into other planes relatively easily. It calls on the greed in every mortal's soul to bring itself forth, and is oftentimes intentionally summoned when a foolish mortal or fey lord wants to purchase something incredibly rare.
The Vendor has existed for thousands of years, acquiring numerous artifacts and magical items in addition to it's endless store of gold and jewels. It also has currency in every conceivable form, from hard coin to promissory notes, from seashells to barter goods. Every civilization with any form of currency has had at least some dealings with The Vendor -- that much it has made sure of. 
The intention for this NPC is to be an inevitable encounter to the PCs. At some point or another, they will be involved with a quest that requires something incredibly rare or even unique. The Vendor will of course have what they need, but will also have a price. It deals both with physical and spiritual currency, and may make several different demands of each member of the party. One may owe The Vendor a favor, one may owe The Vendor their soul upon death to become one of it's wealth-seekers, or even just hard cash should they have it. The Vendor is, while intelligent, very predictable. It has ha

d almost an eternity to know how to swindle mortals, but it will always pursue wealth. If the PCs can offer it something that it could never get anywhere else, its own greed would make it immediately want to pursue that deal.
The Vendor doesn't like combat. Even if it is attacked, the demon will likely just pull itself back into the ground and shift to another plane to conduct further business. If it is absolutely forced to fight, it is an immobile creature. It has many limbs, though most are underground. It has dozens if not hundreds of combat-applicable magic items, so it has virtually any options on the table. Mostly it only wants the wealth of its attackers, and so may only paralyze and rob them. It prefers not to do this when a deal is possible, but The Vendor has been known to do such things in the past.

Quotes:

• "And what do you have to offer?"
• "Your greed…it calls to me….we are not so different."
• Slobbers and fondles gold pieces whenever it receives them.