More information is out, and its just a matter of digging it up, or in this case, going back over it (I missed this one the first time I read it). This reveals a little how C'tans powers work, and the leaked iamges below show off the new Necron Overlord model.
Here is a link to some more leaked images
http://imgur.com/a/32Sp0
http://imgur.com/D3tnybN
Also this is information from the White Dwarf regarding how C'tans work. Consider them rumors until we see the release (always because of possible errors)
via Archibald_TK on Warseer
Regarding the CTans, WD seems to really make a difference between Shards of the Deceiver, Nightbringer, Trans CTan and the Vault. This is how their power work:
- During the shooting phase, chose an enemy unit.
- Roll a D6 or pick a card to determine the attack it suffers.
- The randomness represents the CTan basically doing whatever he wants when released on a battlefield.
- Each attack comes in 2 Flavors.
- The first one, supposedly already devastating, is used by the two shards and the Trans CTan.
- The second one, that appears to be the powerful Apocalypse effect, is for the Vault.