Here is a quick schedule:

Enter the hole in the cliff and wander in the maze. Eventually, pick the Blue Lotus,

Meet the spirit twice,

Look at the hole in the cliff,

Look in the fire pit to get first piece and a key,

Free the prisoner (or not) with the key, I don't know what it brings,

Meet the spirit again,

Kill all the cyclops and make a bridge with the cyclops' bodies to reach the second piece on a small island in SE, or you can give Lotus to Udath or and he'll give you the second piece and die. Then you can flee through the hole, when you come back the cyclops have forgotten what you did...

Meet the spirit again,

Enter the tunnel and investigate a small chamber,

In underground prepare for a hard fight,

Examine the skeleton remains and fight or flee...

... But whatever, don't forget to move lever in the ribcage to stop highwind,

Find third piece (and XPs) in some rubble,

Exit under and view the hole in the cliff to complete circle,

Meet the spirit one last time for XPs and treasure.

After that, you can go back in EC and deliver Lotus.

This quest is hard to reset, I don't know exactly how this works...