Suggestion: if possible, maybe once in a while a horde of monsters raids your base. If you're planning to make an update in which you can upgrade your base, you can add watch towers to scout incoming monsters.
Something's familiar about collecting and evolving monsters. Oh yeah, from five different games. Energy based? Very original... These creators put a lot of time and creativity in making this game.
 "Crush Crush"){kind=icon}
 "Thundercall"){kind=icon}
 "Idle Raiders"){kind=icon}
 "Curio Quest"){kind=icon}
 "Outside, there are 13 kids in spooky costumes"){kind=icon}
 "Shadowbound"){kind=icon}
 "Wartune"){kind=icon}
 "Super Mario Bros. FLASH"){kind=icon}