GeForce and Radeon users aren't the only ones who get treated to beta drivers when new games come out. Intel offers that same service on occasion, too, and it's followed through today with a beta update aimed at Thief and Titanfall. The company is precisely a week late for Thief, which hit stores last Tuesday, and a week early for Titanfall. Batting .500 might be good in baseball, but in software, well...
But I digress. According to the release notes (PDF), Intel's 188.8.131.5264 beta graphics driver update includes "game playability and performance tuning" for both Thief and Titanfall. Haswell-based Celeron, Pentium, and Core processors with Intel HD or Iris graphics are supported, as are Ivy Bridge chips.
You'll find the new drivers on this page for 32- and 64-bit versions of Windows 7, 8, and 8.1.
By the way, keep in mind that Thief's system requirements recommend a Radeon R9 or GeForce GTX 660 graphics card. I doubt that either game will be silky smooth and dazzlingly pretty on any Intel IGP, even with the new drivers. If you're trying to play those games on a Haswell-powered desktop, nabbing a decent discrete graphics card is probably a good idea. (Thanks to TR reader SH SOTN for the link.)
Correction: This story originally said only Haswell processors were supported by the new drivers. Ivy Bridge processors are supported, as well.