After I died something like 25 times yesterday evening trying to defeat the Sphinx I think there should be some adjustment. None of the tactics described above worked for me. Neither staying covered behind the first wall until the Sphinx starts levitating or simply using the old Doom tactic and never stop moving :-)

When I watch this Youtube video it becomes obvious to me that I seem to have invested in the wrong weapon updates and perks ?
https://www.youtube.com/watch?v=SU2mpYjpWaY

The guy kills all the enemies without issues.

Unless someone gives me a hint or difficulty is a bit adjusted this is the end of my Project Warlock travel ;-(
Really a pitty since the game was a lot of fun so far......

I know I'm a wee bit late, but having just beat it I wanted to pipe in.

I think the boss beat me 5 or 6 times, it was very frustrating. On the second last attempt before beating it, I managed to kill it while having 1 hp, and died to the horde of mobs.

I worked out right away that I could stay behind safety in phase 1, and just use the mana weapon thing fully charged, and duck into cover again. The problem with this was that while you're taking your sweet time, monsters keep spawning, and by the time you're ready to start phase 2, there are so many monsters everywhere, that you'll get bogged down, and then owned.

What ended up working for me, was still using that duck and cover behind safety in phase 1, but then spending all my dynamite clearing out the two corners, by throwing dynamite over the walls to where the enemies were to the right and left of your position. Once they were cleared out (you aggro all of them with sort of 2-3 dynamite throws per side), I went for the kill, and circle strafed the whole arena.

I started out using the 90 rounds for the minigun (I have capacity at 1, so I don't have a lot of ammo), and then switched to flamer to clear mobs a bit. Once that was done, I switched to the shotgun and just kept circle strafing around, and finished it. I did switch to the crossbow (upgraded with the piercing mod) once to clear out a few more mobs, but other than that, I just used the shotgun and ran as fast as I could, on the edges of the arena.

Once he died, I finished off whatever was left with dynamite I had picked up while running around. I think my health never dropped below 200 during that final run.

OK, just finished this Boss and as others already said, the fight can be very frustrating and the fear of losing all lives and starting from the beginning would make me drop this game.

In the end, what worked for me was using dynamite on the head in the first phase until it went airborne. As someone already mentioned, if you take the head down fast enough the monster do not spawn in the second phase. I shot 0 mobs during the entire encounter.

For the second phase, I used up all ammo of the upgraded minigun on the floating head and just strafed the entire time while sprinting.

As much as I got my ass handed to me in previous tries, the last try didn't even scratch me.

Hope this helps some of you still stuck on this SOB.

I started playing Project Warlock last week and this post had me worrying that I'd get stuck here at this episode 3 boss fight. Now I'm only playing on Casual, meaning I don't have to worry about lives (I may try another run on Normal afterwards), but I beat it on my first attempt. Details as follows:

My version reports itself as 1.0.2.1 GOG.
My stats were 6, 8, 8, 11.
My perks were Treasure Hunter, Student, Toughness.

I was in running mode the entire fight (I pretty much only use the running speed).

In the first phase I used the Heavy Bolter (upgraded minigun) whilst strafing left and right to avoid the fireballs. I did run out of ammo for it so had to switch weapon. I used the Flak Cannon (upgraded double barreled shotgun).

When the Sphinx moved into phase 2 I noticed the damage he was taking was tiny so I just kept strafing around the map to take out as many of the enemies as I could. At some point I must have picked up some more minigun ammo, which helped with ads, but it was mostly the Flak Cannon at this point. As the number of enemies reduced the boss seemed to take a little more damage. Initially I used the Flak Cannon on him, then I switched to firing fully charged staff blasts at him (I've not upgraded the staff yet).

After that it was just a few moments to pick up as much loot as I could and then to the exit. The game reported a time of about 5 minutes for the level.