well personally i like the planer door option. in a campaign when i was running a lich i had an extraplaner room where i kept my phylactory. (hidden inside one of the bricks witha ward over top) but anyway i had the room sealed inside a mirror with some fake ridle to try and convince anyone snooping around that there was a hidden entrance behind the mirror(ha ha) behind it was another big explosive rune. dm allowed it but there was a pass word or it had to recognize me to let anyone in. also had all kinds of illusionment spells to throw anyone off the track
