Three waves and you almost made it, that's the final wave. After that, you just need to go for the Operator himself, there'll be no more gargoyles.
My base technique
- Make Red Haze and Dancing Star bombs before you go in, at least 10 of each. You can do it without the Red Haze, but the Dancing Star is really useful.
- Buff up with potions (I usually use Golden Oriole, Tawny Owl and Swallow), Cast Quen.
- Once you've got past the dialogue, run behind the nearest pillar, then draw your silver sword. Change pillars and refresh Quen as necessary.
- Throw two Dancing Star bombs at him. This sets him on fire, destroys about a quarter of his health, and makes two gargoyles appear.
- Stay well out of the way, and keep lobbing Red Haze bombs at them. If you don't have the diagram, you can also use Fury/Rage traps (lay them while you're waiting) or Axii. If none of this is feasible, just kill the gargoyles by whatever method you've been using. Keep Quen up, don't take on more than one at a time, and stay well away from the Operator - he's almost invulnerable while the gargoyles are around.
- After the first two gargoyles, if you get the chance, hide behind a pillar again. The Operator is half-blind and may not see you. You can use this time to recover health, and you can even save if he doesn't notice you.
- When you're ready, lob two more Dancing Stars at him again, and repeat the whole thing twice more (a total of six gargoyles, three waves).
- Switch to Steel sword, then go get the Operator. He should be down to quarter of his health by now, and you can continue to use Dancing Stars, but he should be easy enough to take down by sword.
