(In reply to comment #1)
> libGL: OpenDriver: trying /usr/lib32/dri/radeonsi_dri.so
> libGL error: dlopen /usr/lib32/dri/radeonsi_dri.so failed
> (/home/niko/.desura/games/sacred-gold/lib/lib1/libz.so.1: version
> `ZLIB_1.2.0' not found (required by /usr/lib32/llvm/libLLVM-3.4svn.so))
> libGL error: unable to load driver: radeonsi_dri.so

Looks like the game ships its own version of libz.so.1, which doesn't provide
something the system version provides and which LLVM expects, so the radeonsi
(and swrast) driver fails to load, and libGL falls back to GLX indirect
rendering.

Does it work better if you move away
/home/niko/.desura/games/sacred-gold/lib/lib1/libz.so.1 ?

We'd need to see a gdb backtrace of the X server crash, but it's probably
basically a consequence of indirect rendering, which is undesirable anyway.