abstruse

adjective

Definition:

difficult to comprehend

Example:

The abstruse writtings of Malek could only be understood if one knew his previous spell-crafting research.

Personal Commentary:

Here’s another uncommon but useful word for the GM or storyteller. It’s not a dead word by any means, but merriam lists it as a synonym of arcane, while only “related” to confusing. So take that as you will.