Fighting gloom hands in close combat is not recommendable.
I've found and killed King Gleeok yesterday on the third attempt. That was fun and challenging and a nice twist on the standard gleeoks, but the second phase was easy as soon as these icicles dropped in front of me I knew what to do and brought him back down quickly.
Also beat a frost gleeok. Now I just need to beat a flame gleeok, but the only attempt I did so far I got literally nuked in the second phase.