The Tower regularly gives you extra goals to chase beyond simply pushing waves. These challenges are the game's recurring tasks and competitions, and they reward you for playing consistently and improving your tower over time.
The challenges you will run into fall into a handful of categories, each covered on its own page. Tournaments are competitive brackets where your runs are ranked against other players. Events are limited-time activities with their own objectives and rewards. Milestones are long-term goals tied to your overall progress, while Daily Missions are short tasks that refresh each day and encourage regular play. Tiers track your advancement through the game's difficulty ladder.
Use the links on this page to jump to the specific challenge type you want to read about.