The Mirror Shield and Hammer are back in the first Treasure Vault, but you don't need them to get anywhere in any of the main dungeons. There are MirrorRobes in a few rooms - typically those with item cellars - but you don't have to defeat them, you just have to burn the stairway open and get the item.
The only item you need is the wand, which yes, works on those blue enemies. It's actually just a few rooms up from the boss room with those Digdoggers. So by this point, you went halfway around the B6 loop to get to the Digdoggers at the bottom of B7 - but if you continue the B6 loop, there's another set of rooms at the top of B7. The uppermost one has the wand, under a burn stair like the rest of the item rooms. For as many paths as that level stretches, I wanted to be sure the wand, and the enemy it's needed to defeat, were close to each other.
Also, if the compass indicator wasn't clear, all you have to do to get to the boss room and wand item from the start is zig-zag between the upper and upper-right room and take the stairways down until you hit the B6 loop that takes you to both of them.
Double-also, you can get an alternate Hammer, and a better-than-mirror Shield, in the next segment of the game. Or you can just buy a regular Mirror Shield - the shop's at the top left of Underworld - but the cave with the better shield is 3 screens below, so it's probably best to fight through that instead.
[EDIT 2] v1.2 released.
Edited by Lüt, 14 September 2019 - 06:30 AM.