Well, as you see, I have tried to Make Contact, tried twice, but with no result. In this location - Upper Cathedral Ward - you will get new pose "Make Contact" which sends the message "sky and cosmos are one". My simple thinking was, well, if you gave me this pose, probably I should use it to make friends with alien bosses. Unfortunately I have already killed Celestial Emissary, so cannot show him my friendly pose. Ebrietas, Daughter of the Cosmos has completely ignored my friendship.
So with Fire or with Bolt - just kill her. You can select to lock 2 locations on her body - chest (where the chest is supposed to be) or the head. Attacks from behind are safer, however attacks from front may grant you double damage points. Under 50% of HP, Ebrietas will start to throw up the blood and will use ultrasound to damage you when you are inside of the sound ball. Her last resort - a kind of star explosion which will create 3 bunches of projectiles with fast speed and very long range - evade them or you will find yourself dead.
Reward: Great Isz Chalice. Defeat of Ebrietas will also grant you 2 trophies: Ebrietas Daughter of the Cosmos trophy and Chalice of Isz trophy. Great Chalice of Isz.
Good luck and Have a nice game!

Bloodborne Ebrietas Daughter of the Cosmos fight. Bloodborne Ebrietas Daughter of the Cosmos fight tips.

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1st boss: Bloodborne Cleric Fight: https://youtu.be/ubsj6SE5G8o
2nd boss: Father Gascoigne: https://youtu.be/aG654IgWiTs
3rd boss: Blood-starved Beast: https://youtu.be/-3HlvHuOJ6I
4th boss: Vicar Amelia: https://youtu.be/cvyHp6Y7iHE
5th boss: The Witch of Hemwick: https://youtu.be/-p_esxJxqJE
6th boss: Shadow of Yharnam: https://youtu.be/qedjfX1phJA
7th boss: Rom, The Vacuous Spider: https://youtu.be/vhVfQ7gdpso
8th boss: Celestial Emissary: https://youtu.be/yUyGj_R0NpU
9th boss: DarkBeast Paarl: http://youtu.be/5_rlDTawW8s