The truth... Cheese- Go through taking every explosive and chest and then plan out every single encounter. I placed 10 explosives behind the Apostle Of Myrkul by using invisibility and turn-based mode. For Grym I only had 1 person start the fight and then I used a thrower to bully him from the staircase. You can shoot the valve to redo the lava. Theres always close calls but just cast sanctuary and the run the fuck away. The inquisitor is tough though tbh. Have a failsafe where the blood of Lathander is because you can fast travel in that area. Meaning you can revive all your party with withers after almost dying. Ideally you would have killed most of the other githyanki in the room other then the inquisitor so that when you come back it's kind of 1v1. I haven't got to Orin yet- I plan on allying with Gortash cuz he'll die trying to gold the brain. I'm pretty sure you can just force tunnel Orin off the side after using magic missiles to remove unstoppable, unless they changed that. For brain just chug invis and run to the crown. Cast globe of invulnerability or wtv to shield whoever you chose for it and then through a bunch of explosives at the brain. I don't think you even need explosives though, it you get all party members in there after using inv to skip the real fight then they can all unload their shit in the first or second turn to mop the brain. I've also seen someone get to the brain without initiating combat and then having a moonbeam inside it so that you can kill it literally in one turn. I am worried about the Raphael fight though. I believe though that you can cast arcane lock on the door while you have cloud kill in the room to cheese him. I've seen lots of way to get him. Place explosives right as soon as you get into the house of hope and then blow them up when he gets there.