No need to be covert about it. They were made by
VELARD miniatures, and after someone posted about them on Dakka a while back, it took all of maybe 2 days for them to disappear from the page. Gee, wonder why...
As for the actual question of the thread, there really isn't any way to get a
real army out of just those miniatures. Using the Daemonhunters codex, you could easily just take 3 squads of 5 Grey Knights as troops, and Grey Knight termies are allowed to be taken in a squad of 3, although 'fists aren't an option for them, so you'd have to claim those represent their Nemesis weapons. None of that is really a good idea as far as in-game effectiveness goes, due to how fragile those small squads are for their points costs, but that's what you can do with what you have there. I'd reccommend just using the "fire pike" bit as the Psycannon for the squad. Despite the impressive stats of the Psycannon,
GW just models it as a lousy Stormbolter with a single funny-looking barrel, which I always found incredibly lame.
Then you just need to worry about your
HQ and whatever else you want to add. Given the way those Custodes models look, I'd say think about fielding a Grey Knight Grand Master or Inquisitor in termie armor, based off one of the as-awesome-today-as-they-ever-were
old-style Grey Knights models. They'd fit in pretty well, I think.