Go to the North Wing Stacks on the first floor of the Library, then take the teleporter at ( 260, -20, -285 ) /waypoint 260, -20, -285 to the Elemental Portal Gallery. Use the portal at ( 789, 412, -380 ) /waypoint 789, 412, -380.
After killing a veiled sentinel, you get the message, Upon the death of the sentinel, horns sound below you, signalling the start of attacks by waves of marids. There are five waves, consisting of 3, 3, 5, 8, then 9 merids.
The name's spawn is announced by the message, The air grows colder and you hear massive growls. This named has a significant power drain that I have not found a way to defeat. He will also throw you in the air, but you can guide yourself back down to safety unless you were rooted. If you don't have a way to avoid being rooted, this can be tricky.
Once the Champion of E'Ci is slain, a message announces, Upon the death of the champion, you notice a strange sort of bridge spawns between the two towers. Cross the bridge to the south.