I've got an idea for a reusable event. Every night(Or whatever you are doing, mining, dungeon crawling, lab exploring, whatever), you can go on a fighting spree against mobs, these come in three difficulties
Stroll - Easy mode because just taking a stroll and get the heck out of there.
Investigation/Practice - Normal/Medium, investigating for whatever you want, or just training against the mobs.
Extermination - Hard, you could have these end with a boss battle every now and then.
It's just an idea that I came up with after seeing a game mechanic like that. It would probably not work at all, given how events don't work that well here anyways, as seen with the Mechanization, but decided to throw this out there anyways.