This fight is in the northwest of the Queens Garden behind one of the darkness columns. You need the dash upgrade from the Abyss to even get to the fight.
The fight isn't particularly hard. You fight a couple Mantis traitors and then Cloth shows up to help. You need to do damage but can kite the boss if your health gets low and Cloth will finish them off. The full screen wave attacks he does you need to dash through.
The corpse run on the other hand is quite annoying. If you find yourself dieing, grind up 900 essence and then go to the Seer. She'll give you a teleport ability (it costs 1 essence, but it also buffs the chance for you to get random essence so it's essentially a wash). Drop your beacon outside the fight by holding Y + DOWN and you can just port back instantly on death.
If you need big essence drops (you shouldn't if you've kept up with it) and have the moth wings, there are harder versions of the Crossroads boss and the Crystal Caves boss right next to their arenas you double jump into. They're worth hundreds by themselves and are trivial to get back to (especially Crystal Caves since the first version of the boss sits on the bench).