Well since "sufficiently advanced technology is often indistinguishable from magic"you can get away with having some "magic" traps and items be heavily implied to just be barely disguised modern tech with a slight magitech coat of paint to them. Which can also justify the use of modern clothing by having be some "ancient" fashion.
Though at the end of the day though just remember you don't need a complex reason for every addition as most people will just go on with things like suspiciously modern clothing in a medieval setting as long as it's halfway believable. Not saying thought shouldn't be put into this though, just pick your battles and overfocus on something that many not be worth the effort.