This mod is from TaigaUppercut (from GVZ)/VindictusMods (from Youtube), so the credit goes to him.
There are 3 Tieve transformations: Winged, Oracle and Casual. The instructions are also in the readme. I will post pictures of all three of the transformations soon.
Download one of the mods below. Rename the launcher.dll file in en-US/bin to anything else, like launcher-orig.dll, then paste the launcher.dll from the bin folder in the download into en-US/Bin. If you don't already have a folder named data in en-US, create one now. Now post the Materials and Models folders from the download into en-US/data. Now you can go play with your new mod =P
To uninstall just replace the launcher.dll and delete the data folder.
Credits:
@wescooldude3 for the launcher and directions
TaigaUppercut/VindictusMods for these three amazing transformations
Checkbox for good stuff light
Many others, all of which are in the readme.txt
If you want this mod get them from the original forums