Tabu, the Voodoo Shaman was rumored to be a new champion, but is now considered cancelled. Tabu may be based off of the DotA champion, Voljin, The Witch Doctor, and may have been reworked into what is now Swain.
On the 2010 Harrowing map, a coffin, (on the extreme lower right), can be seen containing him, along with Averdian and The Plant King. This could be interpreted as the "nail-in-the-coffin" confirming his cancellation. His name is a play on the word 'taboo'.
Render and Textures
Him in the coffin
Note: Images, names, and descriptions extracted from the game files.
Tabu's voodoo vibes disrupt his enemies' powers, sapping their strength.