Backtracking to pig pen, no waypoint

Hi, I'm new, trying to collect the pig pen waypoint and I can't seem to get there from a5 town or the ascent.
Where do I go or how do I get back to this area?

What waypoint?

The slave pens I think. And I have never missed this waypoint but I always assumed you could walk back up the ascent and make another portal but it sounds like you tried that.

Unless this is for the achievement you can safely ignore that waypoint though. It is is functionally useless once you make it to the a5 town

Ya, primarily this was a question for the achievement, but also seems strange that it's a location that you litterally can't go back to without the waypoint. Why even have a waypoint in an area that you need to manually click on if there is no way to back track and access the location later?
For the person that asked, yes, the slave pen waypoint at the start of A5.

So if anyone knows another method to manually get there, feel free to share it haha

If I recall correctly, after you kill High Templar Avarus in Act5 "something" will happen that will drastically change the Act map, making some previously unaccessible areas accessible (the Ossuary, Cathedral Rooftop and the Reliquiary, not sure on the latest) and some other no longer accessible from the main plaza - one of these will be the Slave Pen. You can still access the Slave Pen via Waypoint (otherwise, you would not be able to return back to the Overseer Tower at all), but you won't be able to reach it again by foot in the aftermatch of that "something"

Short story is: If your Oriath Square is a clean one where Karui slaves club to death scared Oriathans running amok, it will be possible for you to backtrack to Slave Pens. If your Oriath Square is... way less clean, then waypoint will be the only way

Party with a friend who has the waypoint. Have him/her go there and open a portal.

You CAN get to the Slave Pen waypoint by rerunning The Ascent (Act 4). The resonator will still be there and you are able to click on the lever to open the portal.

I have just tested it out. It works.

Thanks! I guess I went the wrong way in Ascend zone and instantly thought I couldn't get there anymore.