Nicely done. Shard spiral gives similar results for magic builds. If you line the legs up just right, you can get two staggers in a row from the same shot, one on each leg.
Golden Order Seal +10, 60 intelligence, 60 faith, the new Pest-Thread Spears incantation from the DLC (maybe the normal Pest Threads spell from the base game works as well) and then perhaps the Flock's Canvas talisman to raise the potency of incantations (by +8 percent). My seal has a spell buff of around 350. I think you can get about the same buff with the Erdtree seal at +10 and only leveling faith to about 80 (so you need to spend less levels in sum than if you use the Golden Order Seal, the Golden Order Seal only gets better than the Erdtree seal at very high levels in both INT and FAI).
Gg! Also, cool character! I tried to respond to your post before, but RU-vid won't seem to let me. Didn't want to leave you hanging though. I'm a huge fan of surrealism in games too. Anyway, good luck with Elden Ring! This looks like a really cool fight!
Wow second phase is brutal bc she is so aggressive. I used mist for first phase, but I noticed that if you don't lock on to her when casting she tends to mainly just walk around, so you can kite her into the mist without being attacked much. Not sure how much difference it would do in 2nd phase though, never even tried mist there.