I have only seen Morpho minion drop 1 time and it was my first try. However it is a roll of the dice even if it does drop. Meaning if Morpho minion does drop you have a 1 in 4 chance of obtaning the Morpho minion. The Morpho minion does NOT!!! drop everytime you run the dungeon. It also gives me something to look forward to; Well collecting tombstones for my ilvl 230 and 260 gear.