I have a slightly alternate method. Using the EGB attack the first Wraith & bring her health down until 1 more hit will kill her. Quickly repeat this process as you head right until you reach the last Wraith on the far right. Then drop straight down the hole to the left of the last wraith & another Wraith under the bridge will agro towards you as you land at the bottom. Quickly take her health down & head left across the pit & climb the ladder to another Wraith. Quickly bring her health down, but get ready because ALL the Wraiths that you just attacked & agroed will not be far behind. Quickly use an Essence item & start killing them as fast as possible. After killing all of the Wraiths that were flowing you, head left on the otherside of the ladder to the cliff edge to find your last Wraith. Quickly lure her closer to solid ground so you can quickly kill her before you Essence item runs out. You can either walk back to the altar or kill yourself to repeat the process.

goes up over 900xp per ghost with the "Hungry Essence" item

nice ! i recomend to let the last ghost kill you so you dont waste time coming back to the checkpoint !