Ebrietas, Daughter of the Cosmos
After reaching the Lumenflower Gardens, you can shatter the window near the lantern and continue down to the Altar of Despair. Waiting for you there is Bloodborne's own flying spaghetti monster: Ebrietas, Daughter of the Cosmos.
Ebrietas isn't difficult to damage, but she hits very hard: about two hits will do you in. You can circle around her and attack her body, but you can deal serious injury by attacking her head - the trick is hitting it. Her swipes and grabs are easily avoided with a back step, but you'll need to clear to the side if she swings her tentacles over her head. If she rears back for a charge, you'll also need to clear out of the hard-hitting path. Also watch for her face-planting attack. Move out of the way, then use the free moment to attack her soft head. At a distance, she may also spit blood at you. Keep moving to avoid being hit.
When she hits half health, Ebrietas will power up, giving her a name rage attack - you'll have to keep sidestepping to avoid the many claw swipes and tentacles slashes. She also gain a flying charge attack, so you'll have to dodge in the same manner as her ground charge. Finally, she may create a cluster of stars over her head. When this happens, staying sprinting and dodging, as the stars will shoot right at you like laser beams.