I would like to use a wizard as the enemy. I've done that before but this time is different: his class level will be above the group's level. As with any other wizard in the world he has to use a spellbook.
This spellbook is my problem because in this specific case I don't want it to be part of the reward. This wizard's spells list will be significantly different from the party's wizard. I usually let him learn some spells this way but in this case it would be too much.
This wizard knows the party and seeks revenge on them so it makes perfect sense that he has prepared things to avoid his spellbook falling into their hands if his plan fails.
How can my NPC wizard ensure that his spellbook is destroyed when he dies?
Note:
I plan to use a 10th level wizard with access to 5th level spells but he is part of an organization that can have access to almost any resource.
As for my game sources I use the 3 core rulebooks, Volo's Guide, Xanathar's Guide and Mordenkainen's Tome.
Best Answer
Thanks to the resources of his organization, this wizard has a contingent fireball cast upon the spellbook. (This makes use of the 6th level contingency spell). The contingency spell is keyed to go off upon his untimely death. (The fireball can be cast at 3rd, 4th, or 5th level and still be used with the contingency spell).
The result utterly destroys the tome and provides a 'last laugh' from the fallen mage.
Spell references:
Fireball (PHB p. 241-242)
Contingency (PHB p. 227)