The bonus objective for this Battle Chest mode is to defeat 3 Sunflower Queens.
Battle Chest description
Sunflower Queens are having a tea party, and you weren't invited.
Beep Boop -
RSVP confirmed. Please wear any cool hats, facial hair, and/or jewelry to Funderdome to authenticate coolness.
- Beep Boop,
Z-Tech Bouncer Bot 108238-Z.
As this is a Crazy-difficulty Battle Chest mode, enemies will deal full damage without any damage reduction, which means that you can die rather quickly if you're not careful. In this mode, the Sunflowers tend to constantly heal the Sunflower Queens, making close quarters combat difficult, so it's best to take out the Sunflowers at a moderate range with characters such as Engineer with his Heavy Helper and Bullhorn Swarm, which can make it easier to take them out without getting killed.