This is my strategy to survive to round 40+ in Shadows of Evil!
Doing the Nero's ritual first, then going to whatever place that has jug, and opening the ritual there, opening the rift and buying the vesper off the wall, saving points for jug, buying it and then doing the ritual, then, I'm doing the rest of the rituals.
Setting Up (Perks, Weapons, etc.)
I'm training at whatever place that has the box and setting up Widow's Wine, then Quick Revive, and then Double Tap, after that I'm building the shield and the Apothicon Servant, and just training with it at the rift, my secondary weapon will be the Ray Gun, that I'll try to get off the box, and if not the Ray Gun, I'm using PaPed Vesper with Dead Wire or Blast Furnace, whatever I gets first.
I'm holding the Apothicon Servant when I'm training in case I'll get trapped and I'll have to use it, and then when all the zombies are grouped and no one can hurt me from behind, I'll start shooting the hoard until its dead. At Round 30+ I'm attacking only with the Apothicon Servant and using my secondary only in case I'm out of ammo until the max ammo, if there is no gobblegums that can help me in this situations and there is one zombie without max ammo, I'm trading it to the box and trying to get it again.