Tripping the Rift - Help !

[MM622]

I'm in Templar Base and need to complete the Main Quest - Tripping the Rift

When I arrived to Fleet Street, I entered into the Red Portal then I'm in Ludgate Hill.

In Lugate Hill, I killed a lot of monsters and saw one group of people there then I entered to the Ancient Blood.

Ancient Blood look like a temple, and I've open all the gate in front of the statue (about 3 to 4 statues). After this, I left the Ancient Blood and return to the Lugate Hill, I saw another group of people there, when I get close to them they start to kill the monster together with me. So, what should I do next to complete this quest? I tried to open the Hellrift Reveal inside the Ancient Blood and Ludgate Hill but it seem not the quest want me to do.

[Madwolf]

you have no need to go in red portals to do this quest.
Go to ludgate hill and use the small blue hellrift detector you should have got as a quest item, at the bottom left of the screen a radar should appear with dots on. run around until a dot is in the middle of the radar, then use the hellrift revealer- if you did this right, things should appear- kill these and repeat this on all the other radar dots.

[MM622]

you have no need to go in red portals to do this quest.
Go to ludgate hill and use the small blue hellrift detector you should have got as a quest item, at the bottom left of the screen a radar should appear with dots on. run around until a dot is in the middle of the radar, then use the hellrift revealer- if you did this right, things should appear- kill these and repeat this on all the other radar dots.

I have done this right as you explained. I turn-on the Hellrift Detector and saw some grey color dots (3) on the radar. Then I run around until a dot is located centre of the radar, then I right-click the Hellrift Revealer. However, no monster is appear. But when I done this, I already killed all other monsters (who use gun and sword) in Ludgate Hill, should I killed them all first then detect the grey dots or leave some monster there first? Is this a problem I can't see the things appear?

[Madwolf]

i don't think it matters whether you kill everything in the area first or not, what i do is enter ludgate, turn on the detector, kill things in area near dot then stand so the dot is exactly in the middle of the radar then use the revealer and kill the two things which appear.
if the dot is not exactly in the middle of the radar, the revealer does nothing. i suggest you put the revealer on the quick bar then use it repeatedly near a dot, moving slightly between uses, you should get something appearing eventually.