You ran into ‘Evolved Gorgotha’. A mob from an extra quest in Khaziel that gives access to a unique hero weapon.
I believe you had to finish all Khaziel quests and at least the first Adana quest to gain access to the extra quest in Khaziel. Back in the days he came with 3 Rock Worms. The unique weapon was either Fire and Ice or War and Peace, I dont quite remember.