Boss descriptions contain story spoilers for the main campaign and bonus stages.
Fast answer
The answer before the background
There are six commonly documented bosses: Nazeru, Quincon, Umbra, Leviathan, Vasile, and Xyzzy. The first three belong to the main campaign, while Leviathan, Vasile, and Xyzzy are tied to additional campaigns or standalone stages. Nazeru appears after wave 14, Quincon and Umbra after wave 15, Leviathan and Vasile after wave 15, and Xyzzy at the start of wave 15. For reliable clears, build high-damage Mage and Archer specialists, protect them from boss disables, reserve Rain of Fire for clustered minions or a boss vulnerability window, and avoid depending on melee troops against bosses with healing or aura attacks.
Roster
All six bosses and their encounter conditions
The main campaign contains three boss stages. Nazeru is the first boss at Nazeru's Gates. Quincon follows at the Temple of Saqra. Umbra waits at Emberspike Depths and is the final boss of the main story.
Additional content adds three more named bosses. Leviathan is fought in The Sunken Citadel during the Rising Tides mini-campaign, Vasile appears in Dusk Chateau during Shadowmoon, and Xyzzy rules Darklight Depths, the standalone Saurian stage.
Bosses generally do not behave like ordinary enemies. Several appear only after the normal wave sequence, while Xyzzy joins the last wave itself. This timing matters because selling a low-value tower or changing rally points before the boss arrives can create a large damage increase.
- Nazeru: Nazeru's Gates, after wave 14. He summons Lesser Efreeti, disables towers with sand, and can instantly kill nearby soldiers.
- Quincon: Temple of Saqra, after wave 15. He jumps between positions, throws explosive barrels, and receives healing from the Warlord King.
- Umbra: Emberspike Depths, after wave 15. He teleports, becomes invulnerable on the plateau, and summons Shade Elementals and Shreds of Darkness.
- Leviathan: The Sunken Citadel, after wave 15. Tentacles disable shoreline towers, and he later breaks pillars and summons Bloodshells.
- Vasile: Dusk Chateau, after wave 15. He fights in two phases, heals through Blood Drain, and gains a lethal Death Aura in phase two.
- Xyzzy: Darklight Depths, at the start of wave 15. He is fast, armoured, and uses a multi-hit ground-smash attack.
| Boss | Main threat | Best response |
|---|---|---|
| Nazeru | Instant-kill attacks, tower disable, Lesser Efreeti | Use concentrated Mage and Archer damage; keep disposable soldiers away from the exit. |
| Quincon | Movement, explosive barrels, healing support | Use ranged damage and artillery; do not rely on barracks to hold him. |
| Umbra | Teleporting invulnerability and summoned dark enemies | Kill summons quickly, attack during the vulnerable path phase, and save abilities. |
| Leviathan | Shoreline disables and Bloodshell wave | Place key damage towers away from the water and use sustained area damage. |
| Vasile | Healing bite and second-phase Death Aura | Prefer ranged heroes and towers; avoid melee units near his second route. |
| Xyzzy | Fast movement, medium armour, ground smash | Use armour-piercing Mage damage, focused artillery, and a late defensive choke. |
No verified boss-specific equipment, currency bundle, or random loot table is documented for these encounters. Defeating a boss completes its stage and may award the associated achievement. Some stages also unlock later campaign locations or show a post-battle story scene.
Strategy
How to beat the main campaign bosses
Nazeru is usually the least complicated boss mechanically, but his summons can cause the real failure. Build enough physical damage to control Lesser Efreeti, then concentrate Mage damage on the boss. Keep soldiers away from him when possible because he can transform or eliminate them. Rain of Fire is strongest when it hits Nazeru and a dense group of minions together.
Quincon punishes a barracks-heavy layout. His jumps interrupt blocking, while the Warlord King's healing makes slow damage inefficient. Crossbow Forts, Archmage Towers, and artillery give better coverage than melee troops. Let artillery handle Mandrilos and other clustered enemies while ranged towers follow the boss across the map.
Umbra is the final boss, but the stage is a battle against his summons as much as against him. Shade Elementals and Shreds of Darkness can threaten the exit while Umbra is untargetable on the plateau. Build overlapping damage zones along the route, keep the hero near the most dangerous summon lane, and avoid spending every ability before the boss leaves his invulnerable position.
- Use Mage towers against bosses with no magic resistance, especially when the boss has substantial health or armour elsewhere in the wave.
- Use Crossbow Forts when you need reliable physical damage, broad range, or rapid shots against mixed enemy groups.
- Keep Barracks for controlling ordinary enemies unless the boss specifically benefits from being blocked.
- Save Rain of Fire for the boss, a summon cluster, or the moment several dangerous enemies overlap.
| Problem | Counter |
|---|---|
| Boss disables towers | Spread important damage towers instead of placing every specialist beside one shoreline or choke point. |
| Boss summons minions | Prioritise the summons if they can leak; a boss that pauses or teleports is often less urgent than an enemy near the exit. |
| Boss heals | Use burst damage and multiple firing angles so the boss cannot recover faster than you damage it. |
| Boss becomes untargetable | Do not waste cooldowns. Clear the active enemies and prepare the route for the next vulnerable phase. |
The tower choices above are practical recommendations, not mandatory solutions. The game supports several successful hero and tower combinations, and difficulty, upgrade choices, and platform balance can change the most efficient build.
Bonus stages
Leviathan, Vasile, and Xyzzy counters
Leviathan disables towers next to the shoreline, so treat coastal build spots as expendable. Put your most important damage farther inland, then use Rain of Fire and area damage when his slow movement brings him into overlapping ranges. He pauses while disabling towers, creating a useful damage window. When he reaches the pillars, prepare for the Bloodshell surge rather than focusing only on the boss.
Vasile is dangerous because his fight has two distinct phases. During the first phase, his bite can kill soldiers and restore his health. After he retreats and returns as a bat, the Death Aura makes nearby troops and heroes unsafe. Ranged specialists and ranged heroes are safer than melee blockers. If the second route is not already covered, reposition towers before the transformation finishes.
Xyzzy combines speed, armour, and a large ground attack. Build an early damage network rather than waiting for his wave to start. Mage towers are valuable because they bypass his medium physical armour, while artillery helps thin the Saurian force around him. Saurian Nightscales can use invisibility, so keep a detection-capable or durable defensive point near the exit and do not assume every enemy is visible.
- For Leviathan, keep critical towers away from shoreline-adjacent positions.
- For Vasile, do not plan to stall the second phase with ordinary troops.
- For Xyzzy, prepare for the boss before the final wave and protect the exit from invisible Saurians.
- The in-game encyclopedia is the safest reference for enemy abilities when a platform uses different naming or display conventions.
| Stage | Encounter timing | Priority target |
|---|---|---|
| The Sunken Citadel | After wave 15 | Bloodshells and other leaks while Leviathan advances. |
| Dusk Chateau | After wave 15 | Vampiresa groups, then Vasile while maintaining ranged safety. |
| Darklight Depths | Start of wave 15 | Xyzzy's approach and Saurian Deathcoils or invisible Nightscales near the exit. |
The documented stealth concern in the later Saurian content is Saurian Nightscale. Because stealth behaviour and detection presentation can differ by release, verify the enemy card in your copy rather than relying on a universal tower list.
Planning
Rewards, completion time, and what is not verified
Boss victories are progression milestones rather than loot encounters. Confirmed rewards include the stage clear, campaign progression where applicable, and named achievements such as Genie in a Bottle for Nazeru, Kongicide for Quincon, and I'm the Lizard King for Xyzzy. The main campaign also ends with the achievement for defeating the Dark Lord and saving the realm.
The official store description advertises hours of gameplay, but it does not give a fixed time to beat the campaign. A precise completion estimate would depend on difficulty, retries, Heroic and Iron Challenges, bonus stages, and whether the goal is simply to reach the ending or to clear every achievement. No reliable official source was found for a single universal playtime.
Community pages sometimes list exact health and damage values. Those figures are useful for comparison, but they vary by difficulty and release. Treat the in-game enemy card and the active platform build as authoritative when numbers conflict.
- For a first clear, choose a lower difficulty if you are learning boss timing rather than testing a build.
- For full completion, include Heroic and Iron Challenges and the bonus stages; they are separate from simply finishing the main campaign.
- Do not expect a boss chest, character unlock, or random item drop unless your specific release explicitly shows one.
| Goal | Verified expectation |
|---|---|
| Finish the story | Defeat Umbra at Emberspike Depths. |
| Complete the boss roster | Clear the three main bosses plus Leviathan, Vasile, and Xyzzy. |
| Earn boss achievements | Defeat the named boss associated with each achievement. |
| Estimate playtime | No single official completion-time figure is published. |
The roster and encounter locations are well documented, but exact numerical stats, bonus-stage availability, and release timing can differ between mobile and Steam versions. This guide avoids presenting one platform's values as universal.
FAQ
Common questions
Who is the first boss in Kingdom Rush: Frontiers?
Nazeru is the first boss. He appears at Nazeru's Gates after wave 14, outside the normal wave count, and summons Lesser Efreeti while disabling towers with sand.
Who is the final boss?
Umbra is the final boss of the main campaign. He appears at Emberspike Depths after wave 15. Lord Malagar is part of the story setup, but Umbra is the boss the player must defeat to finish the main campaign.
How do you beat Umbra?
Build overlapping damage along the main route, clear Shade Elementals and Shreds of Darkness quickly, and save Rain of Fire or hero abilities for Umbra's vulnerable movement phase. Do not waste cooldowns while he is invulnerable on the plateau.
Are there invisible enemies?
Yes. Saurian Nightscales are the key stealth threat documented in the later underground content. Keep a durable defensive point near the exit and check the in-game enemy card for the detection rules in your release.
Do bosses drop items or special loot?
No verified boss-specific loot table is documented. Bosses reliably provide stage completion, story progress where applicable, and associated achievements. Any claim of a universal boss item or drop rate should be treated cautiously.
How long does it take to beat the game?
There is no single official completion-time figure. The total depends on difficulty, retries, Heroic and Iron Challenges, bonus campaigns, and whether you are pursuing achievements rather than only the main ending.
Sources
What we checked
Official listings establish current availability and product facts. Community pages are used for mechanics and build history, then labeled separately.
- OfficialIronhide official Frontiers page
- OfficialIronhide official strategy guide
- OfficialSteam store description and platform information
- CommunityBoss roster and enemy reference
- CommunityUmbra reference
- CommunityNazeru, Quincon, Leviathan, Vasile, and Xyzzy references