Priest healer on Lich King normal inside Frostmourne

What can you do with priest healer inside frostmourne on Lich King normal to prevent death?

I tried just healing the guy. I tried just DPSing the spirit with dots/holy fire/mind blast/smite. I tried doing both at the same time.
I've never been able to kill the spirit. I always run out of time and die.

Is there something you can do or it's a certain death if a priest healer is inside?
Is there a way to interrupt the spirit?

Thanks for the help.

Dispell the debuff from Terenas, debuff is called Soul Rip and if you dispell it it interrupts the cast.

You can also spam shackle to interrupt.