I slew Morian and didn't get the achievement... I had received a lot of other achievements before then.  Yer right OP.  It's either a bug and you were right to report it or Willie's right and it's just not hooked up yet during Beta.  Either way, LH is a friggin masterpiece!

Update:

Nothing changed concerning the Slay ... creature achievements. They still do not work.

I also noted that the "Waitung out the clock" achievement doesn't work. I played the whole 800 turns for "nothing" well not the whole, but i did waste the last 200 since i had already won by far.

It is also true, that when you conquest win on the "Last Season" that win doesn't register and you are instead granted the "Channelers do not live forever dialog"

Also the Steam achievement "Defeat a faction" doesn't work. I defeated so many of them and still don't have it.

Oh another odd thing: When I let the turns run out and lcicked on i want to see my rating the game gave me 0 points. I'll rephrase that for you: Z-E-R-O

points.

But when I conquered the last remaining city of altar (which was really just a formality since i had more then 50 times more faction power than him.) I was granted 10000 points rating at the end screen.

This seems off.