Defense against implosion

[Douglas]

Or, you could take a page out of O-chul's book and remove his holy symbol. Redcloak might put a backup one in his pocket due to lessons learned from said O-chul, but he may be too busy trying to make sure you don't run away with Xykon's phylactery to get it out.

Implosion doesn't require a holy symbol.

I doubt that redcloak would prepare implosion every day. I think he only prepared implosion this day because he planned on attacking the resistance which are all mid-level with mid to low fortitude saves.

It's a domain spell for him. His only alternative to it is Summon Monster IX, limited to lawful creatures. Given the choice between Implosion and Summon Monster IX (which almost might as well be Summon Barbed Devil with the alignment limitation), I'd go with Implosion regardless of expected opponent level. Anyone high enough level to reliably make the save is also high enough level to not consider a Barbed Devil to be a serious threat.