Best maps to get to 50

[Piosidon]

For Fathom Crypts the best place to go is A secret passage. You get there through the sarcophagus. I think you must complete all the levels first to enter. The zombies never stop respawning.

[Nightarcher]

For Fathom Crypts the best place to go is A secret passage. You get there through the sarcophagus. I think you must complete all the levels first to enter. The zombies never stop respawning.

I would say it's mire about the placement of the enemies. If you have a good team or are being leveled by a lv56 friend, you'll kill them all far before they respawn.