Swords Bard 7/Thief 3/Fighter 2 with this build and items. I just used the Helmet of Arcane Acuity instead of the Helmet of Grit. I coated my weapon with Purple Worm Poison and activated Phalar Aluve’s Scream prior to clicking on the gate. I also ascended my tadpole in Creche Y’llek.

I started by making one attack with an Arrow of Many Targets against Raphael positioned such that the arrow ricochets into Korrilla, this shot will need Sharpshooter turned off to increase hit rate for the Luck of the Far Realms + Surgeon’s Amulet instant Paralyze. This will also net 4-7 stacks of Arcane Acuity which will also boost the DC of your Illithid Abilities. Next I drop Perilous Stakes which with the boost from AA will have a 70-80% success rate. Now I just lay into Raphael with Sharpshooter/Ranged Slashing Flourish attacks from within 3 meters for instant Crits while reserving a single shot for Korrilla to activate the Elixir of Bloodlust. Use a Bonus Action to apply a Potion of Speed and Action Surge as needed. I actually had 3 attacks left over at the end to eliminate one of the Cambions and cleaned up the rest Round 2.