Board Thread:Mortal Kombat Wiki/@comment-27004474-20150523164616/@comment-27004474-20150523200124

 Onaga * Onaga makes a brief cameo during two of Raiden's visions and is mentioned in Shao Kahn's bio in Mortal Kombat (2011). First point is made under Appearances (however, the second isn't, so.). Pretty obvious.
 * Onaga is most vulnerable to Liu Kang's Bicycle Kick.

And that's all I see for Onaga.