SpongeBob Tower Defense Update 21 – Boss Battles, New Units, Rewards & Codes

Update 21 in SpongeBob Tower Defense brings the most content-packed release to date, introducing boss battles, mythic units, exclusive mounts, and limited-time items that reshape how players progress and compete.

With new achievements and a bonus XP event also live, this is the perfect time to dive back into the underwater battlefield.

Here’s a full breakdown of everything you need to know about the latest update—how the boss battles work, what new units to prioritize, how to unlock the secret mount, and how to redeem the latest code.

Chum Coliseum – Boss Battles Introduced

The biggest highlight of Update 21 is the introduction of Boss Battles, available through the Chum Coliseum.

This new mode challenges players with escalating difficulty and introduces strategic combat layers that go beyond the standard wave-defense model.

How It Works:

You’ll face 16 bosses in total, each with increasing difficulty
Every boss has unique mechanics, meaning a one-size-fits-all strategy won’t work
Winning a boss fight grants exclusive loot and rare item drops
The higher the tier of boss defeated, the greater your chances of pulling rare units

This mode isn’t just endgame content—it also introduces a new grind route for intermediate players looking to unlock units faster.

New Units – Mythic and Limited-Time Additions

Mythic Gladiator Patrick

A powerful unit designed for frontline combat
Combines high defense and strong melee attacks
Versatile enough to fit into most team compositions, from early waves to boss defense

This is one of the most durable units currently in the game, perfect for soaking up hits while other units dish out damage.

Lion Fish (Limited Event Unit)

Available only during this event window
Comes with special abilities that set it apart from standard aquatic units
Its limited nature means it may never return, increasing its value both in gameplay and in collection

This unit is tied to achievements and event crates, so players are encouraged to act fast.

Chariot Mount – New Movement and Stat Boosts

A new Chariot Mount has been added to the Mount Shop, offering both visual flair and functional buffs.

Key Features:

Enhances movement speed across maps
May provide minor buffs to unit placement or skill activation
Themed around Coliseum-style warfare to match the new boss mode

As players begin experimenting with different mounts for tactical positioning, the Chariot Mount offers both utility and style.

Unit Food – New Resource System

Update 21 also introduces Unit Food, a consumable resource used to upgrade or enhance specific units.

Uses Include:

Increasing unit effectiveness during battle
Possibly unlocking new unit abilities (feature still being explored by players)
Feeding favorite units to maximize late-game performance

The introduction of this item opens the door for future mechanics like evolving or prestige systems.

Coliseum Clash Achievements – Unlock the Secret Mount

A new set of achievements under the Coliseum Clash category have been added, encouraging players to engage with the new Boss Battle system in a meaningful way.

Rewards:

Completing all Coliseum Clash achievements unlocks the Secret Lion Fish Mount
This mount is exclusive to players who conquer all challenges tied to the Chum Coliseum
It’s currently one of the few cosmetic items with unlock conditions tied directly to in-game skill

This system rewards not just grind, but precision, planning, and mastery of the update’s toughest content.

Weekend 2x XP Event

To celebrate the launch of Update 21, the developers have activated a double XP event that runs until Monday at 11:59 PM CT.

Benefits:

Level up faster, ideal for catching up on past updates
Unlock abilities and unit upgrades more efficiently
Test new units like Gladiator Patrick in real time without resource pressure

This is a limited window to maximize your account growth.

New Redeem Code – GrowASponge

As a thank-you to the community and a makeup reward for the update delay, a new redeem code has been released:

Code: `GrowASponge`

How to Redeem:

Open SpongeBob Tower Defense
Go to the Settings or Code Menu
Enter GrowASponge and confirm
Receive in-game rewards including resources or event-based items

This code is time-limited, so be sure to claim it before the next major update or seasonal event.

Final Thoughts

SpongeBob Tower Defense Update 21 is a strong step forward for the game, offering depth, exclusivity, and strategic challenge across its new features.

From Gladiator Patrick to secret achievements and the boss gauntlet of the Chum Coliseum, the update is designed to push both casual and hardcore players to engage more thoughtfully with their units and team setups.

With a limited-time XP boost and a free code available, there’s never been a better time to log in, assemble your best team, and take on SpongeBob’s toughest enemies yet.