@Halion: That's awesome, didn't think of using tinker to spot them.
There's another dungeon I found, not sure if new. It contained a level 1 zombie, a monster whistle and a zombie dog. The zombie dog is a single use, small slot item which gives your next attack +30% damage and gives whatever you attack the "undead" attribute. Found repeatedly in the eastern snowy levels (berserkers etc).
@gjaustin: Not lockerable, just found it.
CYDSTEP gave these.
ENDISWAL gave this.
LEMISEE gives one of each seal scroll.
I found that big empty room too. It's completely dark and massive.