This is the Gara-Nui ("Great Liberator" in Matoran). It is a combat/transportation-type vehicle that is operated by a rather intelligent AI and can carry up to 2 Krana and 1 entire Bohrok. In its flight mode, shown above, it can either pilot itself or be controlled by a Krana residing in the Bohrok shell it is carrying. It can also fold out legs and/or sword-carrying arms for battle and use as a walker, making it a TransforMOC of sorts. Again, these limbs can be either self-controlled or controlled by a pilot Bohrok.
The reason for the Gara-Nui's name, as well as its purpose, will be explained in a future chapter of The Chronicles of Xa and Vu when it makes an appearance. You can also download the full set of images for the Gara-Nui, including building instructions and pictures of its humanoid form, here. (No, the patched-together-looking Bohrok riding it in one image is not Xa).
This relatively simple MOC was actually created quite a while ago, and an earlier version may have been posted here under the name "Krana Carrier". It has undergone a few changes since then, though, and will undergo more as the series in which it appears progresses.
Edited by 742mph, Nov 03 2012 - 07:44 PM.