Question regarding background music.

I find the background music for the campaign map for the Crusades campaign
very enchanting.

Does anyone know what instrument it is? Sounds like a lute, lyre, oud or any of those plucking instruments...which I love.

Also if anyone could point me to OST or equivalent, that would be greatly appreciated as well.

If I've understood correctly you're talking about the Persian Santur (<-link).

Spoiler Alert, click show to read: 

The santur is a three-octave wooden-hammered dulcimer with seventy-two strings which are arranged on adjustable tuning pegs in eighteen quadruple sets, nine (bronze) in the low register, and nine (steel) in the middle register. The Santur can be made from various kinds of wood (walnut, rosewood, betel palm, etc.) depending on the desired sound quality. The front and the back of the instrument are connected by soundposts whose positions play an important role in the sound quality of the instrument. Although the santur is very old, it was neither depicted in miniatures, nor presented in any other medium until the nineteenth century. The secret of making the trapezoid-shape sound box lies in the quality and age of the wood, as well as in the arrangement of the soundposts which connect the table of the instrument to its back.
source:http://www.kereshmeh.com/santur.html

Videos of the Persian artist, Shahriar, ENJOY !:
https://www.youtube.com/watch?v=wc0P...eature=related
https://www.youtube.com/watch?v=b9cZ...eature=related
https://www.youtube.com/watch?v=d8bU...eature=related
https://www.youtube.com/watch?v=3OmERWCitGA

I find this one very interesting, fusion, Western Orchestra with Santur:
https://www.youtube.com/watch?v=8NIdn5RJLYk

2 excellent CDs:
"The Sound of the Mughal Court" by Aashish Khan (<-link). Mostly Sarod, but with accompaniment. If you like the Kingdoms sountrack you'll probably like this.
The 2nd one, I've forgotten actually, but this one may be a good substitute: Mystic Journey by Jalal and Soheil Zolfonun. This is setar, but it should have the same "enchanting" background sound.

You have to be a bit choosy if you want the same style as in M2:TW, takes some looking around. There are different melodic compositions.

So it IS a dulcimer-style instrument.
I remember hearing a fantastic Dulcimer performance during a convention in Baltimore, but that sounded quite different from the one I hear in Kingdoms... but thank you so much for the information and I will keep searching.
Kudos to the Persians who came up with such a beautiful sound.

The reason I like the style in Kingdoms BGM so much is that its very similar to the tunes of Korean instrument named gayageum or keomungo...

Thanks for the tip. I'm really into all things Korean at the moment, as I felt a little ignorant on that country's culture. I'm going to look that up.