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 ( 774, 412, -336 ) /waypoint 774, 412, -336 to enter.
Make a note of where the Runic Stones went, because you'll need them during the fight.
Glimmerstone cannot be damaged in the circle of stones where he spawns.
Attack Glimmerstone then go activate and kill a Runic Stone, once the stone has been killed you can pull Glimmerstone out of the circle to damage him. Once he ports back into the stone ring kill another Runic Stone, repeat until he's dead.
Heaper flies off periodically. Follow him and kill his adds.
Heaper apparently gets a buff from the emerald dust from breaking crystals in the Forest Barrens. You may want to go around and break all the crystals yourself before fighting Heaper to prevent him using them. If you destroy all of the crystals, Heaper doesn't fly away. When destroying a crystal you get a buff called Emerald Dusted Weapon which helps killing the mounds and drones.
Or you can dispel or apply a state effect on Heaper to remove his Emerald Dust buff.
Click Heaper's mound near ( 254, 160, 103 ) /waypoint 254, 160, 103 to obtain sticky vekerchiki mud.
Head to the Muddy Lagoon ( -73, 21, 588 ) /waypoint -73, 21, 588.
Kill muddite lurchers, then click the corpses to apply the sticky vekerchiki mud. This spawns a minimud, which you must kill.
Be sure to pull the muddite lurchers out of the water before you kill them (the water tries to compost you).