Boss Hunt is a gamemode currently only found in the Single Player missions. As of now, only two Boss Hunt missions exist; one involves Captain Smasher, and the other involves the Royal Hypno-Flower, but more may come with Trials of Gnomus DLC. Similar to Solo Ops, the player can select up to three AI helpers and can swap the control between them during the gameplay.
Boss Hunt has three phases, with the latter two repeats until the boss is defeated. After the boss arrives, the player must defeat it in 20 minutes (shown as Hunt Time). There are no time limit of revival; the player can revive their characters as long as at least one character is still alive and has enough Hunt Time left.
Bait Defense phase
To attract a boss, the player must place some bait on a table to attract it (Jolly Rogers Candy for Captain Smasher and Strong Coffee for the Royal Hypno-Flower). After the player places the bait on the table, two waves of AI plants or zombies, depending on the mission, will try to attack and eat the bait. The bait has significantly less health than a garden and a tombstone so the player must properly guard it. It is unknown why they made a bait menu if you can only use one type of bait for the boss.
After successfully defending the bait, a short cutscene will play, which involves the boss destroying the bait and the table it lays on while rising/growing out of the ground. After the cutscene ends, the player is allowed to face the boss and the Boss Fight phase begins.
Boss Fight phase
During this phase, the boss can be attacked by the player. The boss will frequently call reinforcements which will spawn multiple regular enemies. Every time a boss loses a fourth of its health, the boss will activate a curse that affects all player characters in some way, and the Curse phase begins. When the boss loses all of its health, the player wins and the player automatically escapes the battle.
This phase is activated every time a boss loses a quarter of it health. During this phase, the boss becomes invincible against the player's attacks, and the player must complete an objective to cure the curse. Each boss have a unique curse. Once the curse is cured, the Boss Fight phase resumes.
Captain Smasher spawns several Cursebearers and the player must kill all of them in 90 seconds, otherwise all player characters die instantly. Royal Hypno-Flower transforms all characters to a goat, and the player must eat all Poly Leaves on the map to restore their original form.
Trials of Gnomus DLC
This update added three new achievements (Boss Battle, Boss Battle Specialist and Boss Battle Boss) that involves beating a Boss Hunt game on multiple difficulty settings. According to the descriptions of these achievements, Boss Hunt could be accessed from the Mystery Portal inside the Town Hall.