Run an event every month with a new in-game leaderboard tracking some particular pve feat. The leaderboard for that feat is active only within that month, and at the end of the month, winners are declared and receive prizes, then the leaderboard clears and starts tracking a different feat for the next month.
As an example, during the month of March, the event leaderboard could be tracking everyone's win streaks against demigods, and the highest streaks in the month would receive prizes at the end of the month.
Feats to be tracked could be basically anything, really. Win streaks are already coded so they're a good place to start, and even if we just cycle through win streak events, there's six targets so it would change frequently. Later on (as more bonuses get coded) can do leaderboards for "highest poison counters achieved", total number of EMs against a target, etc.
Seems like a good way to get more events going on and provides a new way for people to compete. Can also be utilized to test balance details by directing a lot of grinding time at specific targets or to specific deck styles.