Great game just there is some balancing issues as lvl 3 skull book, monestary and succubus I fell are guaranteed wins (especially lvl 3 book with bard) and there are also really bad units like milk man, holy book and viking,(though I could see holy book being good if you add enemies with more damage) also i would love for it to be more clear what the skulls ability is as there is no way to know unless you level it
I have had success with milkman actually especially at level 3 as it gives a shield in addition to the buff. and if you invested in milkman in early levels, then get a really strong unit later, you have the milkman immediately applying to the higher tier unit which can be better than getting (and leveling up) one of the earlier units like the spear guy or the viking which become underwhelming later on their own.