Here is a breakdown of the scoring system for Soulkeep. There are 2 primary factors to scoring. The player's health at the end of each round and the mana score for each mob killed.
First off is player health per round. At the end of every round a player gets 40 points of score per point of health(Hearts). I do not believe this changes based on league level if anyone can confirm. 40 points per round means early mistakes can seriously hurt your long term score potential. Squeezing the legendary spell Heartgiver in on round 1 when possible is key to maxing your score potential here as well as giving you a mob loss buffer before you lose. Heartgiver costs 20 mana points to cast and immediately grants increasingly more extra Hearts or life per level of the spell(3-12).
Next up is the score you receive for killing the mobs before they can escape. Each point of mana earned from killing a mob equals a point of score. Here there are 2 ways we can affect our score, the tower Voodoo Sapper and the spell Mana Mania.
Voodoo Sapper(seen here from captaindingus.. @captaindingus/soulkeep-a-shift-in-the-balance-of-power-rise-of-the-voodoo-tower-hive-153635 ) is a 100 mana legendary tower that grants an increasing boost per level to the mana earned from mobs that it kills starting from 130% to 220%. For this you mostly want to position the few(2) of these you get per map where another tower has already softened the mobs up. This tower hits both land and flying targets and upgraded can 1 shot more different targets on its own.
The other way to increase your score/mana is the epic spell Mana Mania. This 5 mana spell increases the mana earned for each mob killed in it's radius from 110% up to 200%. Higher levels of the spell not only increase the bonus but the spell's duration and how many uses the player gets from 3 up to 5 rounds. Where and when one places this spell might vary for the same map based on the day's random tournament rules. I haven't tested how this reacts with Voodoo Sapper(if they additively/multiplicatively stack or if mobs have a mana cap) if anyone wants to chime in.
Here is the base mana earned per mob as I've been able to determine so far. I do not believe it changes per league level. If someone sees one I messed up please do chime in, I'm trying to eyeball these and sometimes I can't get just 1 mob to die nicely so I can note the mana/score. 😀 Currently this list is missing the boss mobs for league 4 and 5 as well as Greater Crow and the 2 new mobs added in map 5-5. I'm currently in league 5 so any mobs/bosses beyond there I don't know yet either obviously.
Bloodling - 2
Book of Wounds - 3
Cauldron Dweller - 8
Flying Devourer - 1
Lesser Crow - 9
Nightscreecher - 9
Terror Mite - 8
Blood Queen - 23
Pixie - 18
Slaying Mantis - 32
Crystal Hand - 3
Magic Hat - 18
Black Cat - 18
Wraith - 8
Baby Jacko - 17?(might be off here)
As I get some runs with the remaining mobs where I can tell their score, I'll post them. If anyone else knows the score for the missing mobs, can add the score for mobs beyond league 5 or sees an error please jump in and let us know.