This instance has pitfalls hidden all over the map, with mobs waiting susceptible players in the pits (high 70ish triple up). The pitfalls cannot be seen since (well sort of...they do tend to have a slightly different shade if you look carefully, but the edges may not be exactly where you see them) it looks just like regular floor (unless you keep your map or mini-map open).
There are four Named monsters in this zone. The "Keepers" have some minor tricks to their fights (one of them does a periodic mana-drain as you fight it, for instance), but they shouldn't be too hard to take down. After you have killed the Guardian of Eternity, two shards should appear in its room which are to be moved to the altar of dreams and altar of nightmares (the rooms for The Keeper of Dreams and The Keeper of Nightmares). This will unlock the door to the Praetor of the Phylactery.
Upon engaging the Praetor, it will spawn a few adds (coming from its left and right side). If the adds reach him, he heals 20%, so root them or otherwise engage them until the Named drops. The Praetor does have a leash point, so don't back too far off the main platform he stands upon.