Entrance is from the The Sinking Sands, at a partially buried tower on the far side of the zone from the docks ( -208, -100, -617 ) /waypoint -208, -100, -617.
Exit the zone by clicking a white skeleton inside at ( -11, 7, 8 ) /waypoint -11, 7, 8 - this takes you all the way back to the Sinking Sands dock.
Good chronomage mentoring level is 55 (60 will grey out most of the zone except for the named).
Beware The Guardian of Rathmana and The Protector of Rathmana, twin level 55 Epic(x4) ^^^ mobs guarding one of the 4 exit passages. These will vanish after you have killed the other 3 named bosses in the starting area, one at the end of each of the other 3 corridors. They are Nagini, Sirn' Vehn, and Hira' Vehn. Each is a 51^^^, and a couple of them have some bodyguards. There are quite a lot of trash mobs to clear to get to each one.
Continuing then past where the epics were, you'll find Ortallius, a white NPC, surrounded by 6 Orillian Prelates and a huge statue in a shallow pond. The prelates are 50^^^ Heroics, but unlinked, and easy to pull individually. Apparently these cannot be either attacked until the first 3 bosses have died.
When all the prelates have been killed, Ortallius becomes attackable, he's a 51^^^, alone. Killing him spawns the final boss in front of the statue, Rathmana Allin, a 52^^^. She is surrounded by several Orillian Corpses, 51^^. But those are stationary, unlinked, and most are far enough away from her that they shouldn't be a problem. If you try killing them, they will respawn very rapidly (maybe in a minute or so) in other parts of the pool, so this is rather futile..