Mmm....not bad.
I'll always be partial to tieflings being drawn much broader than these 4e vengeance machines with a collapsed empire, but "vengeance machine with a collapsed empire" works pretty okay for a specific tiefling background.
Still not a fan of their physical appearance with the large horns and the 4-5 foot long rigid tails (!?), but that's probably easy to house rule, assuming they don't have horn or tail attacks all over the place in the core.
Their powers are evocative of the "vengeance" theme without being too showy, flashy, or power-y, and they reflect the fluff pretty nicely, even if I do prefer a different fluff.
To complain about a name, "Infernal Wrath" isn't the best for that ability. Something like "Vengeful Wrath" might be better, or even something a bit dirty-sounding like "Grudge Attack." There's nothing particularly infernal about wailing on someone who has wailed on you. "Bloodhunt" is pretty good, though, so it's a bit of a wash.
It passes muster. The races look like they're solid enough to stand up on their own so far, which is neat.
