It is a mighty technique, but the point of this thread is that it is not that 1-shot kill.
You're right that's it's not unlimited damage, and you're right that there are three monsters that can survive it...but every character that beats the Clerics initiative gets a shot in, and the moment the Seal breaks everyone but the Cleric get's their readied actions.
So maybe it's not a one shot kill, but you can still take out Orcus without him ever getting an action, and that makes it an automatic win if it hits.







