I didn't realize this mode has not been added to Tower Defense, so I'm gonna suggest it. Survival mode for Tower Defense. If you guys have played Balloon TD 5, you already know what this is gonna be. But I'll still explain it. In this mode, players don't send mobs against each other. They instead build defense against monsters coming to attack their castle that don't come from players. There are waves and each wave gets harder and harder. And yes, there are bosses in this mode. I was think the wither and giant (possibly the ended dragon). Hope you guys like the suggestion