I mean they are draining their vital energy or something does it reduce pops or happiness or maybe growth ? 

I'm really curious to see how the Vodyani evolve over Early Access, right now they're by far the most unique faction in the game

UndeadPuppy wrote:
That's what I though at first but the description for it doesn't mention any negative effects on the target system.

I just watched a gameplay after a certain ammount of turns all the pops of the enemy faction dissapear. 

Yeah, apparently they're killed and/or made into more Vodyani pops.

I think they are not killing or draining life, but converting other races to golden substance in stylish suits, just like themselves.

And their totally generic population bonus +1 FIDS looks like an evidence.

iDrunk wrote:

...but converting other races to golden substance in stylish suits, just like themselves.

Oh look, we have Horatio already :D