The achievement's description is "Clear cards from Caliph's Tomb (cumulative)." I've won several games of Caliph's Tomb but it still shows 0/100. Is this achievement still available? What do I need to do for it?

As far as I know its still available. However it may be glitched in one way or another. Some achievements keep track in the "background" and once you get to 100 you will get your achievement. Other times its not tracking at all and you won't get it.

You need to check the Bugs forum, under games issues, there should be a sticky topic about achievements. From there, hopefully you'll see the achievement you're looking for and if you need to wait, submit a ticket, or post about it.

Thanks for the advice! I'll do that.