Only problem I got was finding the exit.
After clearing and picking crystal, I searched the cave about 7,5min.
Then I tried to use TP chip to get out, doesn´t work.
Finally hit the T, then I spawned at the exit and the exit arrow apeared next to may
I could not find all of the feffs it seems...I thought I had killed all...ran around in circles to find this chrystal...when I found it in the end I couldn't do anything with it...as if I had missed one or more of 'em...
When I left the cave and reentered, the counter was reset and I didn't feel like doing it again :|