First I spoke with Gurru near High Priest Diru Riwirn . After going thru his dialogue, Gurru sent me to speak with High Priest Diru Riwirn. Thats when I was given the flag for the sewer.
Is there a pre-req for getting a trial from this guy? If not, what do I need to say for him to give me the trial? When I hailed him he said "[long text here.] Please prepare and talk to me again when you are ready to help."
I was alone when I was testing it out: do I have to have a group to get one? If so, is there a minimum number of people in the group like with LDoNs?
If you are getting the message ending in 'Please prepare and talk to me again when you are ready to help.' then you most likely have not received the pre-flag from Scribe Gurru.
In order to proceed with the flags for the Sewers Trials, you must complete the steps in this order: 1. Hail Scribe Gurru and listen to his text for a pre-flag 2. Hail High Priest Diru to get the trial-version of the Sewers Purifying Plant instanced zone. 3. Return to Scribe Gurri after your trial is complete. 4. Procede to the High Priest again and hail him for the next sewer trial in the series. 5. And so on... and so forth... until all 4 trials are completed.
This last sentence is subject to correction: I *believe* but am not absolutely certain that these instanced zones require a minimum of 3 people in group (maximum of 6 people) and I also believe that you cannot zone into any of the instanced zones if you are below L61.
High Priest is North and East of the pyramid where the zonein for the trials are. He is the SE corner of the building at 240,n650. To get the trial, form up your group, run in here invised, drop invis at the farthest SE corner, then just hail him. It should automatically bring up the Expedition window (Alt-Z to open/close) with the correct assigned trial...whichever one the Group Leader has not yet done.
To get to the trials zonein, you have to enter that massive pyramid, circle around to the right inside and enter the back room in the SE corner. The pyramid entrance is on the west side. The sewers zonein is at n335, n640.
Once you complete a trial, you can still do it for exp only again (no boss spawn at the end though) by talking to Gamesh at n380, n710