Personally, I imagined Kindred's ult be like this...

"Lamb and Wolf reunite into one once again - the Power of Chaos resurfaces"

AD and AP are increased by a huge amount

AS/Crit/Apen/Mpen are increased as well...or not, I don't know

CDR is lowered or removed

MS, AA range and QWE range are increased

"However, the Power of Chaos is too great to be fully comprehended and fully contained in a material body"

Armor and MR are decreased by a huge amount (or even becoming 0)

HP decreases gradually and Heath regen becomes 0

I don't what's the best approach to this ult's duarbility, an arbitrary amount of seconds, or until the champ dies. Also haven't decided if one can deactivate the ult prematurely.

Obligatory link here: http://tvtropes.org/pmwiki/pmwiki.php/Main/YinYangBomb

Please do not be too harsh on the criticism. I'm far from an expert in this and only made this based on my understanding and what I've seen for the yin-yang theme and (very little) Taoist philosophy.