What is the "9th" cover on SK.com/Darktower

[Andro]

Hello, quick question - while poking around the website, I decided to visit "The Dark Tower" page. In "The Books" section, there are 9 different book covers. I recognize DTI - DTVII, along with WTTK, but what is the "9th" book cover, sandwiched between DTVII and WTTK? In other words, the middle of the bottom row, below Wolves? Looks like a doorway on the beach....just curious, appreciate the insight!

[Brian]

Its the Limited of Little Sisters.

[GNTLGNT]

...I think this is the one.....

[champ1966]

The Little Sisters of Eluria

[Andro]

Thanks everyone!!