I see!

So, good news, there is !pixeldungeon@lemmy.world which has slow but steady activity.

I guess !slaythespire@lemmy.ca also fits that definition. You can maybe post there to see if people would be interested in a Faster than light or Roguelites community. !gaming@lemmy.world can be a good place to ask too.

What you really want to avoid is create a community and then having no one coming there, which will probably make you drop the idea after a few weeks.