It’d be nice if you added some NPC kingdoms that would attack you every now and then, and if defeating them then you can get some coins! They should attack by levels from 1-15.
Level 1: Atk 1-5lvl
Level 2: Atk 6-8lvl
Level 3: Atk 9-10lvl
Level 4: Atk 11-14lvl
Level 5: Atk 15 – 16lvl
ETC
