HoN got the idea from diablo III's king leoric which is skeleton king from DotA.
Since they took ra's resurrection idea from king leoric from DotA and Icefrog took king leoric from Diablo I, they decided to make an updated leoric from Diablo III as the alternate avatar for Ra.
And so... all i can say is.... for a warcraft model, this is very badass!!!
Edit: Can you make a pure king ra version of this? Just wondering. xD