Help! I have tried and tried to get through the portal by the Teleporter in the Underlife. I cannot figure out who the "Unique Guardian" is!! Who can help me?

The Underlife is a bit confusing to most players. Basically, it works like this:

1) You die in a Shadow's Embrace subdungeon and end up in square area with a quest NPC and 9 gates.

2) Only one of the gates can be opened. That gate is determined by the subdungeon you were in at the time you accessed the Underlife.

• After you go through the gate, you'll enter an open area and have a number of mobs to kill. One of these mobs is the "Unique Guardian" for it's specific area. Upon killing it, two additional gates open: 1) One to the Ninja NPC who will grant you a reward for turning in a quest item and 2) a gate to a teleporter that will take you back into the subdungeon from which you originally came.
• You cannot open any other gates. They will all either state that they can't be opened by any means or that the Unique Guardian must be defeated.

I thought that one could access the entire Underlife zone if one were to access it from every single SE subdungeon and kill every one of the Unique Guardians for every single room, but it didn't work that way. While testing it, I ran all of SE in a single play session, never resetting instances, and killing the Unique Guardian in every instance of Underlife I unlocked. Unfortunately, none of those instances are connected to each other. As such, I still couldn't enter any of the other chambers in the Underlife other than the one for each respective instance.