D&D 5E Whelm and Blackrzor should they be wielded by the ones guarding them also Keraptis to fight or not to?

[Nightbeat84]

Good day everyone like to pose 2 questions. The Vampire and the Oni protecting the treasures in White Plume mountain its not stated that there wielding the weapons in combat vs the PC's but was thinking why not ? I know that there quite powerful but would it be to hard for a group of 4 level 9 PC's to overcome them? Also was thinking that if the PC's want to fight Keraptis at the end that I should but from the sounds of it he might be a Lich which would be to much for them to handle in straight up fight. I was thinking of having the Efreet but Keraptis as well but only really as a illusion of some kind or some kind of weak clone maybe but different support monsters for him so when and if they defeat him he will either turn to dust or revert back to something like a doppelganger with some spell casting ? If the PC's interrogated the fake he can said he is under mind control magic to keep an eye on hes place while hes out like security guard and that the real Keraptis is somewhere else. On the other hand if the PC's collect the magic weapons would it balance it out enough that they could have a chance vs a solo lich Keraptis? Any thoughts or ideas would be appreciated. Going to be running white plume mountain in 2 or 3 weeks from now.

 

[Voadam]

Some good inspiration for what's going on with Keraptis can be found in Return to White Plume Mountain.

 

[Eltab]

You could have Keraptis' Phantasmal Force get into a fight with the PCs, and when they defeat it the real Keraptis voice-overs "I will retrieve those which are mine..."
Have the PCs occasionally encounter creatures from inside the dungeon (spies!), until they are tough enough to face the stat block you think Keraptis should be. He finally shows up when they are trying to get out of somebody else's dungeon.