Obviously a reference to the eclipse, any thoughts?

Or maybe he meant "dark son"? Could be Sylar. lol

Yep, here (in the speculation forum). Episodes 10 and 11 are "The Eclipse".

(it's a 2-parter...)

The black sun also has a correlation in the conspiracy world. I know 'dark sun' is not the same thing, but those that believe in the Saturnalian cult think that the black sun is a symbol of the Illuminati.