The New Best Weapon? Blasphemous Blade Location After Patch 1.03 | Elden Ring 

An actual full guide on how to get the weapon step for step. You sir are a rare breed and I thank you for taking the time to actually SHOW everyone how to get this weapon instead of just teleporting to the boss room.

Just killed this boss pretty simple with the right setup. I have been running a mage build. Get yourself the death poker, this is the meat and potatoes of your DPS Mimic ash +10, no spells except rot spell. For the flask, I used HP Regen and HP recover when low health Had 8 health pots and 5 mana (or 6 if your focus is not 180+) Have the fire damage mitigation talisman on, and others that helps mitigate, or help buff your health, the fire damage mitigation is very important. Phase 1 - use rot to chip away at his health over time, it does a ton of damage since it's based on % of HP so you should be doing 100+ a tick. Summon your mimic and run in the lava, pop your flask so you can heal while you are right up his business Spam ghostflame ignition over and over, the damage interruption actually helps you recast faster while the previous cast is still doing damage. Do this over and over and he goes down in about 2 minutes. Repeat for phase 2, rot, then run in and spam. Boss dead in another 2. He had around 30500 health since the damage never stopped, haha

Wait so you dont have to do the quest to get it now?

😭 ｐｒｏｍｏｓｍ