From personal experience, Ravens seem to show up every 5-6 floors in Delves. If I get a Raven on floor 250, I won’t see one till floor 300+. However, I wonder if this is because of two different factors:
- Ravens show up based on how many floors you’ve done. This is similar to other events. For instance, invasions you will get a Raven every 3.8 battles, on average, which means spending 500 gems to get 20 sigils will always yield around 168 towers (20*4 = 80, but you get a raven every ~3.8 battles, which gives you 8 more towers).
- Or Ravens are based on how many total rooms you’ve done in between the last Raven. This would prevent players from seeing a Raven, killing it, skipping to the boss, then in the next two floors, skipping straight to the boss. This is a strategy I’ve used, on the basis that ravens aren’t going to show up on these floors, so why bother killing all the rooms when I’m only trying to get to 500 (pet). But if it looks at total rooms cleared, not floors, then skipping to the boss on any level increases the time between ravens.
It takes a lot of extra time to do full clears on every level, so being able to skip to the boss on at least 3 floors after a raven is found is incredibly beneficial. Around 4-6 floors above the last raven, I start full clearing until I find another raven. But would I encounter ravens MORE often if I did full clears on every floor?