it's not a group hunt instance, so i assume only solo.
just let out mount lvl 8 or 10 mount would be ok, many players do it when they are lvl 6.
it has 10k+hp but not so hard, i never did it cause i dont have the deck of cards to open it.
in the instance it rewards fragments of a golem pet, which can be assembled for a pet or traded with gnome NPC for gnome coins (not valuable ones).
also you'd get fiery heart from boss drop if you have learnt the guide book