Defeat Cazador without Astarion (possible SPOILERS)

[StarScepter]

This is my 3rd run, and my first without Astarion. I never had him in the Party, as I chose to Respec Gail to Arcane Trickster Rogue (since that is the punishment Mystra did to him for his infidelity). Now I am in the late stages of Act 3 and am trying to prevent Cazador from Ascending. My Party is rather powerful, but we are unable to take down Cazador before he Ascends. And once he Ascends he seems to be near unbeatable. Any and all help, hints, or outright SPOILERS are welcome. Thanx!

[hermit0wl]

Take a bunch of summons with you and place them on the ritual circles in front of the spawns. It blocks the ritual.

[Brian_the_Brute]

Attack from a distance before he speaks, don't let him get the villain monologue in. All you really need for this fight is globe and a few offensive spells like disintegrate, chain lightning, etc. to target Cazador. Hunger of hadar and/or ice storm in front of you will occupy and damage the grunts while you are safe and sound in your globe.

[RollerPig]

I think you need to kill one of the ritual sacrifices to make sure he doesnt ascend if Astarion isn't with you.

I have beaten him ascended. I actually ran away at first because he basically one shot lea'zel.

I came back fully buffed up, snuck up on him with invisibility and killed him. Definitely use range and necrotic resistance. Took 2 rounds to kill him with EVERYONE buffed, elixired and hasted. Honor mode

just be ready to invis and book it up the stairs if things go bad

[Estevan Valladares]

Take Astarion with you, and have in our group some highly mobile and hard single target hitter.

Leave Astarion back up the stairs and start the fight, so the fight will go on as if Astarion is not there, the single out Cazador by backing up at range. When you are close and should be at a "reasonable level", it will be easy to position so Astarion can come out of the rotation and "unfairly" change the battle.

After that, mop up and let things go.

If you are built and high level enough, you can even do it in steps by introducing each member of the group in the fight gradually, shaping the battle to expose him to demise.

What is important is start the fight without Astarion "aggroing".