How Boss Waves Work and How to Beat Them
A boss wave tests everything your defense has been doing up to that point. A single enemy with a huge health bar arrives, often with escorts, and your towers need to deal enough focused damage to bring it down before it reaches the exit. Bosses also remove many lives if they leak, so one failed boss wave can end a run that was going perfectly.
The good news is that bosses in our games follow consistent rules. Once you know them, boss waves become something you prepare for, not something you survive by luck.
The rules every boss follows
- A large health bar shown on screen, so you can track progress.
- Phases at 66 % and 33 % health. Bosses change behaviour as they cross these thresholds.
- Telegraphed abilities. Before a dangerous ability, a warning marker appears. The effect follows the warning, which gives you time to react.
- Half resistance to slows. Bosses resist half of every slow.
- Heavy lives cost. Every enemy that reaches the exit removes lives equal to its strength, and bosses remove many.
Where you will meet bosses
| Game | Boss(es) | When |
|---|---|---|
| Kingdom Defender | Warlord | Wave 15 |
| Crystal Defense | Hollow Titan, Crystal Devourer | Waves 10 and 20 |
| Space Defense | Dreadnought | Wave 15 |
| Zombie Defense | Abomination | Wave 15 |
| Medieval Castle Defense | Siege Tower | Wave 16 |
| Robot Defense | Overseer | During the 18-wave run |
| Jungle Defense | Ancient Stomper | During the 18-wave run |
| Endless Defense | A boss | Every 10 waves |
| Boss Defense | Bulwark Golem, Swarm Mother, Storm Wyrm, Void Colossus | After 5 build-up waves per stage |
Prepare before the boss wave
Because you build before each wave and the wave only starts when you press Start Wave, the wave before a boss is your preparation window. Use it:
- Know the wave number. Boss waves are fixed, so you can plan several waves ahead.
- Invest in single-target damage. Splash and chain are great against crowds, but a boss is one target. Heavy hitters such as the Ballista, Railgun, Sniper and Longshot, or high-damage upgrades, do the real work.
- Answer the boss's defenses. If a boss is armored, use armor-piercing or damage-over-time towers; damage over time ignores armor. If it has shields, Tesla and Lightning style towers deal double damage to shields.
- Set heavy towers to Strongest. With the boss on the field, Strongest targets the highest-health enemy, which will almost always be the boss. Keep cheaper towers on First to handle escorts.
- Turn off auto-start in games that have it (Quick Defense and Endless Defense) so you do not roll into the boss wave before you have finished building.
During the fight: phases and telegraphs
Watch the health bar. As the boss crosses 66 % and then 33 %, expect a change in behaviour. Many players find it useful to drop the game speed to 1× or pause (Space) when a phase threshold approaches, so they can see what the boss does next.
When a warning marker appears, you have a short window before the effect. What you do depends on the boss, but the principle is the same: the telegraph is information, and the best defenses are built so that no single ability can break them.
Boss Defense: four bosses, four lessons
Boss Defense is built entirely around this. Each of its four stages has five build-up waves followed by a unique boss:
- Bulwark Golem has shield phases. A shield bar absorbs damage before health, so plan for extra damage during those phases, and favour shield-breaking damage wherever it is available.
- Swarm Mother summons more enemies. Splash and chain damage must clear the summons while single-target towers stay on the boss.
- Storm Wyrm makes telegraphed dashes, which cover ground quickly. Build depth along the route so the defense still has damage waiting after a dash.
- Void Colossus uses a telegraphed EMP that disables towers. Spread your damage out rather than relying on a single cluster that one EMP can switch off.
Robot Defense teaches a similar lesson with its EMP Storm wave event, which knocks random towers offline briefly. Redundancy is what keeps a defense standing.
Abilities are boss tools
Games with active abilities let you save your strongest tools for the boss:
- Crystal Defense: Meteor is a targeted area strike, useful on a boss surrounded by escorts; Frost Nova slows everything, though the boss resists half.
- Hero Defense: War Cry gives towers +50 % damage for 8 seconds. Fire it when the boss is deep inside your densest kill zone, not as it enters the map. Rally heals the Warden and restores 2 lives if something leaks.
- Space Defense: the station shield absorbs leaks and recharges between waves, so keep the Shield Overcharge ability in reserve for the Dreadnought wave.
Slows against bosses
A slow that works well on normal enemies is only half as strong on a boss. A 40 % slow becomes 20 %. That still adds time in range, so a slow near your heavy towers is not wasted, but do not count on it. The best use of slows during a boss wave is often controlling the escorts. See how slow towers work for the full maths.
If the boss is about to leak
- Use every ability you have left.
- If the boss survives but you are still in the game, spend everything before the next wave on heavy damage near the end of the route. Selling a badly placed tower returns 70 % of its total cost to help pay for it.
To practise with a single, predictable boss, try the Warlord in Kingdom Defender. When you are ready for more, Crystal Defense's two bosses and then the four stages of Boss Defense will test every part of this guide. For keeping your lives intact through tough waves, read how to protect your base.
