Idea for game (add only if you want to)
In [] only additional things that maybe too hard to make.
If you will want to add campaign with 3 levels 1st its graveyard walls 1 row of health and tutorial for 1st game (kings son comes after graveyard walls destroyed do not give gold but 1 purchase in shop be free of lvl2 unit [cant be spell, item or building]).
(or any other theme of levels can be) after beating level units saved and for 1st fight next level +3 gold.
2nd kings city walls 3 rows of hp walls destroyed do not give gold but 2 puchase in shop be free of lvl2 item or spell [cant be building or unit] (every start of battle wall archer shot randomly dealing 1 damage +1 per row of wall hp taken, and wall guard comes after wall destroyed guards nearly ally adds +1 damage up to guard deaths ).
3rd kings castle 4 rows of hp (after every line of castle hp destroyed lowers lvl of random witch's unit [if on unit item takes that item instead of lvl lovering] [cant be spell, building, skull, mage or succubus]).
(If dev of Necro Chess have any questions to idea free to ask).
These idea originally for Necro Chess.
Have a good day and thanks for reading.