I got to round 28 on solo, died because of the last 2 zombies i stupidly ran into them, but id like to share my strategy as i dont think anyone has found out the trick i got to get the bowie knife at round 2-3 so here goes;
at round one i straight away check what power up is through the door, we want a double points mainly, a max ammo will probably do, then i open the first door let all 6 zombies come in, then shoot the zombies once each if there is a double points.
Then become the beast, open the first ritual room and activate the crane turn on quick revive and open the door, when you come back pick up the pen and shoot the shadow men then knife the zombies, usually once a zombie is injured and you become the beast it doubles the zombies so you get 12 zombies in one round, knife them all.
At that point you should have around 1000 points, then round 2 let the zombies come in again, there should be around 10 zombies, shoot them 3 times in the body each, open the door towards the boxing ring, then become the beast and turn on the power to the perk machine and whatever else you need to up there then hit off the other item to the boxing ring ritual.
here you should now have around 20 zombies to stab but before you do go back and collect that double points through the door, knife them all, gain a few extra points also by doing up the windows every round as every few point count.
You should pretty much have enough to get the bowie knife at this point, so just knife zombies from there, then go do the first ritual, just train them in a circle if any get infront of you just knife them as its a one knife kill.
then kill the last zombie, go to round 3 play as normal, by just knifing leave a zombie, then open the area to the vesper (which is personal choice as i like the vesper) then buy the vesper and do the boxing ring ritual, you can shoot the shadow men for extra points but easier to survive by just training them.
then kill the monster and you gain 2000 points for the ritual and monster, then go onto the bext ritual etc... Until they are all complete, you should be able to end the round with almost 5000 points, enough to get jug and then get the train to find the symols for the egg.
once youe got all the symbols, end the round by the source of the egg and as soon as your able to become the beast zap the symbols and get the egg also knock the box open with the statue.
start chaging it in the statue by the boxing ting as that is the hardest place to survive, remember to just knife.
you should be able to charge that and get to the next statue, which is in the rift, place it there and kill the last few zombies.
round 5 - you should be able to charge the egg up on another 2 statues this round, then do the last one at round 7- as the flies dont count as souls, you will then have the sword.
before ending the round start the upgrade for the sword as its better to get it out the way with as the rounds are still early, and then at the end of every round do the next step and you should have an upgraded sword by the end of round 12.
this is by far the best and probably easiest way to get your game started so you can start training in the rift, you should also have enough points to open all doors and get all fuses and upgrade your gun.
if you get a nuke in early rounds it may take you a little longer.
My game went like this;
round 2 - bowie knife
round 3 - all rituals complete, bowie knife, jug.
round 4 - retrieved the egg right at tge start and put in statue, got nuke staight away so went to round 5
round 5 - charged egg in rift and in the statue towards boxing ring, then went to start charging by vesper.
round 6 - fly round, got quick revive and stamin-up
round 7 - chaged egg by vesper and over the brdge by the water.
round 8 - got the sword right at the beggining, done the first upgrade challenge at the end of the round.
round 9 - exploding balls.
round 10 - end of round completed the next step to upgrading sword.
round 11 - upgraded vesper, 10,000 points.
My internet connection went at this point so i cant update any further, this is the best way to start off as you could get the upgraded sword by end of round 11 if everything goes good.
so at round 11 i had - jug, stamin up, quick revive, all rituals complete, all fuses retrieved, retrieved the sword and complet 2 of the four steps of upgrade, and could have completed the third step that round, and also upgraded the vesper and had about 8000-10000 points still to use.
Sorry for the lengthy guide just wanted to break it down, please if anyone tries this, let me know if this is successful for you.
Thanks In Advance,