Upgrades in Kingdom Rush are used to increase the power and effectiveness of towers and spells. There are six upgrade trees, one for each tower type and one for each spell. Each tree has a total of five upgrades.
Stars
Upgrades are bought with stars, which can be obtained in several ways:
- Completing a Campaign level gives stars based on the number of lives left:
- 18+ lives: 3 stars
- 6-17 lives: 2 stars
- 1-5 lives: 1 star
- Completing a Heroic Challenge or Iron Challenge gives 1 star.
- Exclusive to the Flash version:
- Buying the Premium Content gives 15 stars.
- Clicking on the Twitter and Facebook buttons gives 1 star each.
- Trivia
- You need to get 65 (62 stars on Flash) stars to buy every upgrade on all six trees in the original Kingdom Rush.
Kingdom Rush
Archer Tower
Salvage (1 Star): Marksmen Towers return 90% of value when sold. (Normally a rate of return is 60%.)
Eagle Eye (1 Star): Increases Marksmen attack range (by 10%).
Piercing Shots (2 Stars): Piercing shots ignore a portion of the enemy's physical armor. (1/4)- Far Shots (2 Stars): Increases marksmen attack range (by 10%).
- Precision (3 Stars): Marksmen attacks have a chance of dealing double damage. (10%)
Piercing Shots (2 Stars): Piercing shots ignore a portion of the enemy's physical armor. (1/4)
Far Shots (2 Stars): Increases marksmen attack range (by 10%).
Precision (3 Stars): Marksmen attacks have a chance of dealing double damage. (10%)Barracks
- Toughness Training (1 Star): Barracks train soldiers with more health. (+10% health)
- Better Armor (1 Star): Barracks train soldiers with improved armor. (+10% armor)
- Improved Deployment (2 Stars): Improves rally point range (by 20%) and reduces soldier training time. (Respawn time is reduced by 3 seconds for Holy Order, and by 2 seconds for the others.)
- Endurance Training (2 Stars): Barracks train soldiers with even more health. (+20% health of the main one)
- Spiked Armor (3 Stars): When attacked, soldier's spiked armor return a 10% of the damage to the attacker. Spiked Armor also affects Reinforcements and Heroes. (dealt as True Damage)
Toughness Training (1 Star): Barracks train soldiers with more health. (+10% health)
Better Armor (1 Star): Barracks train soldiers with improved armor. (+10% armor)
Improved Deployment (2 Stars): Improves rally point range (by 20%) and reduces soldier training time. (Respawn time is reduced by 3 seconds for Holy Order, and by 2 seconds for the others.)
Endurance Training (2 Stars): Barracks train soldiers with even more health. (+20% health of the main one)
Spiked Armor (3 Stars): When attacked, soldier's spiked armor return a 10% of the damage to the attacker. Spiked Armor also affects Magic Tower
- Spell Reach (1 Star): Increases wizard's attack range (by 10%).
- Arcane Shatter (1 Star): Magic attacks destroy a potion of enemy physical armor on every hit. (-3% armor per hit, doesn't work on enemies with physical damage immunity.)
- Hermetic Study (2 Stars): Mage Towers construction and upgrading costs are reduced by 10%.
- Empowered Magic (2 Stars): Increases wizard's attack damage. (about 15%)
- Slow Curse (3 Stars): Magic attacks slow enemies by half their speed for a moment (half a second, Arcane Wizard the whole one-second beam duration. Also disables Rocket Rider Turbo boost).
Spell Reach (1 Star): Increases wizard's attack range (by 10%).
Arcane Shatter (1 Star): Magic attacks destroy a potion of enemy physical armor on every hit. (-3% armor per hit, doesn't work on enemies with 
Hermetic Study (2 Stars): Mage Towers construction and upgrading costs are reduced by 10%.
Empowered Magic (2 Stars): Increases wizard's attack damage. (about 15%)
Slow Curse (3 Stars): Magic attacks slow enemies by half their speed for a moment (half a second, Arcane Wizard the whole one-second beam duration. Also disables Rocket Rider Turbo boost).Artillery
- Concentrated Fire (1 Star): Increases artillery attack damage (10% damage increase).
- Range Finder (1 Star): Increases artillery attack range (by 10%).
- Field Logistic (2 Stars): Artillery construction and upgrading costs are reduced by 10%.
- Industrialization (3 Stars): Artillery special abilities costs are reduced by 25%.
- Smart Targeting (3 Stars): Artillery suffers no reduction of splash and chain lightning damage. (Means the damage is not reduced by distance from the center of explosion or between targets of Tesla x104 electric bolt.)
Concentrated Fire (1 Star): Increases artillery attack damage (10% damage increase).
Range Finder (1 Star): Increases artillery attack range (by 10%).
Field Logistic (2 Stars): Artillery construction and upgrading costs are reduced by 10%.
Industrialization (3 Stars): Artillery special abilities costs are reduced by 25%.
Smart Targeting (3 Stars): Artillery suffers no reduction of splash and chain lightning damage. (Means the damage is not reduced by distance from the center of explosion or between targets of Rain of Fire
- Blazing Skies (1 Stars): Adds 2 additional meteors and increases meteor damage.
- Scorched Earth (2 Stars): Meteors set the ground on fire burning enemies over it for 5 seconds.
- The Fast & Furious (3 Stars): Increases meteor damage, explosion radius by 25% and reduces cooldown by 10 seconds.
- Blazing Earth (3 Stars): Doubles damage and duration of scorched earth, and reduces cooldown by 10 seconds.
- Cataclysm (3 Stars): Increases meteor damage and rains 5 additional meteors at random locations all over the battlefield.
Blazing Skies (1 Stars): Adds 2 additional meteors and increases meteor damage.
Scorched Earth (2 Stars): Meteors set the ground on fire burning enemies over it for 5 seconds.
The Fast & Furious (3 Stars): Increases meteor damage, explosion radius by 25% and reduces cooldown by 10 seconds.
Blazing Earth (3 Stars): Doubles damage and duration of scorched earth, and reduces cooldown by 10 seconds.
Cataclysm (3 Stars): Increases meteor damage and rains 5 additional meteors at random locations all over the battlefield.Reinforcements
- Well Fed (2 Stars): Well Fed Farmers have additional health and deal a little more damage. (50 HP, 1-3 damage)
- Conscripts (3 Stars): Conscripts have more health and are better equipped. (70 HP, 10% armor, 2-4 damage)
- Warriors (3 Stars): Warriors have even more health and are excellently equipped. (90 HP, 20% armor, 3-6 damage)
- Legionnaires (3 Stars): Legionnaires have the most health and wear the best equipment. (110 HP, 30% armor, 6-10 damage)
- Spear Throw (4 Stars): Gives Legionnaires a spear throw attack that can target ground and flying enemies. (110 HP, 30% armor, 6-10 damage, 24-40 ranged damage)
Well Fed (2 Stars): 
Conscripts (3 Stars): 
Warriors (3 Stars): 
Legionnaires (3 Stars): 
Spear Throw (4 Stars): Gives Legionnaires a spear throw attack that can target ground and flying enemies. (110 HP, 30% armor, 6-10 damage, 24-40 ranged damage)Kingdom Rush: Frontiers
Archer Tower
- Steady Hand (1 Star): Increases marksmen attack range (by 10%).
- Lumbermill (1 Star): Reduces basic archer construction costs. (-10 gold for level 1-3 archer towers).
- Focused Aim (2 Stars): Increases marksmen attack damage. (1-2 damage).
- Accuracy (2 Stars): Increases marksmen attack range (by 5%) and damage.
- Twin Shot (3 Stars): Marksmen have a chance of shooting two projectiles at the same time. (10%)
Steady Hand (1 Star): Increases marksmen attack range (by 10%).
Lumbermill (1 Star): Reduces basic archer construction costs. (-10 gold for level 1-3 archer towers).
Focused Aim (2 Stars): Increases marksmen attack damage. (1-2 damage).
Accuracy (2 Stars): Increases marksmen attack range (by 5%) and damage.
Twin Shot (3 Stars): Marksmen have a chance of shooting two projectiles at the same time. (10%)Barracks
- Defensive Stance (1 Star): Barracks train soldiers with better armor. (+10% armor)
- Boot Camp (1 Star): Barracks train more resilient soldiers. [HP +10%]
- Esprit de Corps (2 Stars): Increases barrack rally point range (+20%) and healing rate (+20% per second).
- Veteran Squad (2 Stars): Soldiers are trained faster and with improved armor. (-2 seconds of respawn time, +10% armor of the main one)
- Courage (3 Stars): While in combat, soldiers, mercenaries & reinforcements regenerate health.
Defensive Stance (1 Star): Barracks train soldiers with better armor. (+10% armor)
Boot Camp (1 Star): Barracks train more resilient soldiers. [HP +10%]
Esprit de Corps (2 Stars): Increases barrack rally point range (+20%) and healing rate (+20% per second).
Veteran Squad (2 Stars): Soldiers are trained faster and with improved armor. (-2 seconds of respawn time, +10% armor of the main one)
Courage (3 Stars): While in combat, soldiers, mercenaries & reinforcements regenerate health.Magic Tower
- Rune of Power (1 Star): Increases mages' attack range (by 10%).
- Spell Penetration (1 Star): Mages' bolts have a chance to ignore magic resistance. (10%)
- Eldritch Power (2 Stars): Increases mages' attack damage (by 10%).
- Wizard Academy (2 Stars): Reduces mages' special abilities costs by 10%.
- Brilliance (3 Stars): For every other mage tower built, each mage tower gets a bonus to damage (+5% per tower beyond the first, to a maximum of +30%).
Rune of Power (1 Star): Increases mages' attack range (by 10%).
Spell Penetration (1 Star): Mages' bolts have a chance to ignore magic resistance. (10%)
Eldritch Power (2 Stars): Increases mages' attack damage (by 10%).
Wizard Academy (2 Stars): Reduces mages' special abilities costs by 10%.
Brilliance (3 Stars): For every other mage tower built, each mage tower gets a bonus to damage (+5% per tower beyond the first, to a maximum of +30%).Artillery
- Smoothbore (1 Star): Increases artillery attack range (by 10%).
- Alchemical Powder (1 Star): Artillery has a chance of dealing maximum damage with no splash reduction.
- Improved Ordnance (2 Stars): Increases artillery attack damage (by 10%).
- Gnomish Tinkering (3 Stars): Reduces artilleries' special abilities reload times.
- Shock and Awe (3 Stars): Artillery towers have a 20% chance of stunning their targets for 2 seconds on every attack.
Smoothbore (1 Star): Increases artillery attack range (by 10%).
Alchemical Powder (1 Star): Artillery has a chance of dealing maximum damage with no splash reduction.
Improved Ordnance (2 Stars): Increases artillery attack damage (by 10%).
Gnomish Tinkering (3 Stars): Reduces artilleries' special abilities reload times.
Shock and Awe (3 Stars): Artillery towers have a 20% chance of stunning their targets for 2 seconds on every attack.Rain of Fire
- Burning Skies (2 Stars): Increases meteor damage and reduces cooldown by 5 seconds.
- Scorched Earth (2 Stars): Meteors set the ground on fire for 5 seconds, burning enemies walking over it.
- Hellfire (3 Stars): Adds 2 additional meteors and reduces cooldown by 5 seconds.
- Conflagration (3 Stars): Increases meteor damage and explosion radius (+25%) while doubling scorched earth effects.
- Cataclysm (3 Stars): Increases meteor damage and rains 4 additional meteors at random locations all over the battlefield.
Burning Skies (2 Stars): Increases meteor damage and reduces cooldown by 5 seconds.
Scorched Earth (2 Stars): Meteors set the ground on fire for 5 seconds, burning enemies walking over it.
Hellfire (3 Stars): Adds 2 additional meteors and reduces cooldown by 5 seconds.
Conflagration (3 Stars): Increases meteor damage and explosion radius (+25%) while doubling scorched earth effects.
Cataclysm (3 Stars): Increases meteor damage and rains 4 additional meteors at random locations all over the battlefield.Reinforcements
- Trained Volunteers (2 Stars): Trained Volunteers have additional health and deal a little more damage. (50 HP, 1-3 damage)
- Men-at-Arms (3 Stars): Men-at-Arms have more health and wear good armor. (70 HP, 10% armor, 2-4 damage)
- Champion (3 Stars): Champions have even more health and wield great weapons. (90 HP, 20% armor, 3-6 damage)
- Sworn Blades (3 Stars): Sworn Blades have the most health and wield dual weapons. (110 HP, 30% armor, 6-10 damage)
- Recurve Bow (4 Stars): Gives reinforcements a ranged weapon that can target ground and flying enemies. (110 HP, 30% armor, 6-10 damage, 16-30 ranged damage)
Trained Volunteers (2 Stars): Trained Volunteers have additional health and deal a little more damage. (50 HP, 1-3 damage)
Men-at-Arms (3 Stars): Men-at-Arms have more health and wear good armor. (70 HP, 10% armor, 2-4 damage)
Champion (3 Stars): Champions have even more health and wield great weapons. (90 HP, 20% armor, 3-6 damage)
Sworn Blades (3 Stars): Sworn Blades have the most health and wield dual weapons. (110 HP, 30% armor, 6-10 damage)
Recurve Bow (4 Stars): Gives reinforcements a ranged weapon that can target ground and flying enemies. (110 HP, 30% armor, 6-10 damage, 16-30 ranged damage)Kingdom Rush: Origins
Archer Tower
- Master Shooter (1 star): Increases Archer attack damage.
- Treesinged Bow (1 star): Increases Archer attack range (by 10%).
- Obsidian Heads (2 stars): Archers deal maximum damage against unarmored targets.
- Elven Training (2 stars): Improves all Archer special abilities.
- Bloodletting Shot (3 stars): Archer attacks have a 15% chance of causing heavy bleeding.
Tower Maximum Bloodletting Damage Hunter Arbor 23 (22 iOS) Watcher Arbor 23 (22 iOS) Sentinel Arbor 46 (44 iOS) Arcane Archers 46 (44 iOS) Golden Longbows Long-range shot: 161 (154 iOS)
Long-range shot combined with a "crit": 299 (286 iOS)
Short-range shot: 69 (66 iOS)
Short-range shot combined with a "crit": 115 (110 iOS)
Barracks
- Elven Fencing (1 star): Reduces basic barracks construction costs. (-10% for level 1-3 Barracks)
- Expert Tactician (1 star): Increases barracks rally point range. (by 20%)
- Enchanted Armor (2 stars): Barracks equip soldiers with improved armor. (+10%)
- Moon Forged Blades (2 stars): Soldier attacks deal 15% additional magic damage.
| Tower | Damage without Upgrade (with Upgrade) |
|---|---|
| Defender Barracks | 1-4 (3-5) |
| Warden Barracks | 3-7 (5-9) |
| Ranger Barracks | 8-12 (11-14) |
| Bladesinger Hall | 11-14 (14-18) |
| Forest Keepers | 24-36 (30-42) |
- Blessing of Elynie (3 stars): Soldiers have a 10% chance of cheating death when dealt lethal damage. (Soldiers revive with full health when proced.)
Magic Tower
- Crystal Focus (1 star): Increases Mage attack range. (+5%)
- Empowered Magic (1 star): Increases Mage attack damage. (+17.5%)
- Crystal Gazing (2 stars): Increases Mage attack range (+5% from crystal focus)
- Unstable Magic (2 stars): Mage attacks have a small chance of dealing triple damage. (Each bolt gets 5% chance and it is shown as a "BLAST!".)
- Alter Reality (3 stars): Mage attacks have a chance of teleporting enemies 20 node back down the path.
Druid Tower
- Hardened Boulders (1 star): Increases Druid attack damage. (+10%)
- Sharp Splinters (1 star): Increases boulder explosion area.
- Earth Mastery (2 stars): Increases Druid attack range. (by 10%)
- Heavy Load (3 stars): Boulder explosions ignore physical armor.
- Shocking Impact (3 stars): Boulder explosions slow enemies for a short time. (by 50% for 0.5 second)
Thunderbolt
- Thunderbolt (2 stars): Adds 3 additional thunderbolts.
- Roaring Gale (2 stars): Increases thunderbolt damage and reduces cooldown by 10 seconds.
- Thunderstorm (3 stars): Adds 2 additional thunderbolts, while heavy winds slow down all enemies.
- Monsoon (3 stars): Increases thunderbolt damage and doubles wind slowing effect.
- Furious Tempest (3 stars): Increases thunderbolt damage and casts additional bolts at random enemies.
Reinforcements
- Skilled Defenders (2 stars): Skilled defenders have more health and better equipment. (60 HP, 3-5 damage, 20% armor)
- Elven Stars (3 stars): Gives reinforcements a ranged weapon that can target ground and flying enemies. (60 HP, 20% armor, 3-5 damage, 7-10 ranged damage)
- Green Wardens (3 stars): Green Wardens have more health, better armor and improved weapons. (100 HP, 35% armor, 5-10 damage, 10-20 ranged damage)
- Rapid Response (3 stars): Reduces reinforcements cooldown by 5 seconds. (From 15 seconds to 10 seconds.)
- Moon Sentinels (4 stars): Moon sentinels are elite elven huntresses, riding giant panthers. (150 HP, 50% armor, 10-15 damage, 20-30 ranged damage)
Kingdom Rush: Vengeance
Upgrade Points
Upgrades in Kingdom Rush: Vengeance are bought with Upgrade Points instead of Stars and are gained differently to previous games. Unlike in previous games, upgrade points are exclusively earned from Campaign mode; completing Heroic and Iron Challenges give no upgrade points. The number of upgrade points earned is independent of stars; no matter how many lives the player finishes the stage with, the number of upgrade points is always the same. Most stages grant three upgrade poimts upon completion, with the exception of the following:
- Kazan Mines, Jokull's Nest: 4 upgrade points
- Otil Farmlands: 6 upgrade points
- Denas's Castle: 10 upgrade points
Towers
- BLITZ TACTICS (1 upgrade point): Increases the bonus gold for calling an early wave. (80% additional gold)
- WAR RATIONS (1 upgrade point): With a full belly, Barracks units have improved health. (30% additional HP)
- GXR-1 TARGETING SYSTEM (2 upgrade points): Improved with Goblin technology, Archery towers gain extra range. (5% additional range)
- BIGGER BOMBS (1 upgrade point): Infused with powerful alchemy, explosions now have a bigger range of effect. (20% additional area of effect)
- RUNES OF POWER (2 upgrade points): All mage towers have a slight chance of dealing double damage on each attack. (10% chance of double damage)
- GUILD OF MERCHANTS (2 upgrade points): Costs of towers' special skills is now reduced. (15% cost reduction)
- MASTER ARCHITECTS (2 upgrade points): All towers gain extra bonus damage. (10% additional basic attack damage)
- DEATHRAY COILS (4 upgrade points): Replace the flags on each exit with deadly tesla coils that zap incoming enemies. These coils can zap enemies every 180 seconds for 150-300 true damage.
Heroes
- BACK TO BATTLE (1 upgrade point): Reduces the respawn time of Heroes. (10% respawn reduction)
- SPECIAL TRAINING (1 upgrade point): Thanks to a secret and intense training heroes level up faster. (25% extra XP gain)
- ONE MAN ARMY (2 upgrade points): All heroes improve their base attack damage. (15% extra damage)
- ULTIMATE POWER (1 upgrade point): All heroes' Ultimate skills now have their cool downs reduced. (20% CD reduction)
- IRON WILL (2 upgrade points): All heroes improve their maximum health. (20% HP increase)
- SHIELD OF PROTECTION (2 upgrade points): Every basic attack inflicted to a hero has a small chance of dealing no damage. (10% chance to trigger)
- SECOND WIND (4 upgrade points): Heroes now have a small chance of instantly respawning. (10% chance to trigger)
Demon Goonies
- INFERNAL COMBUSTION (1 upgrade point): After dying, Goonies explode dealing area damage to all affected enemies.
- TRAINED GOONIES (2 upgrade points): Better trained for combat, Goonies now have improved health and damage.
- DEMON GUARDS (3 upgrade points): Goonies are now Demon Guards! They are capable of withstanding huge amounts of damage. Mutually exclusive with Hellion Tridents.
- INFERNAL NOVA (2 upgrade points): Demon Guards now die with a bigger explosion. Deals extra damage and reaches more enemies.
- HELLION TRIDENTS (3 upgrade points): Goonies are now Hellon Tridents! They are demons that can hit their enemies with a ranged attack. Mutually exclusive with Demon Guards.
- FLAMING TRIDENTS (2 upgrade points): Hellion Tridents now throw burning tridents that burn enemies on impact for a brief duration.
- PIT LORD (6 upgrade points): When reinforcements are called to the battlefield, now there's a small chance of summoning a Pit Lord with them.=
Soul Impact
- EXTRA IMPACTS (2 upgrade points): When the spells cast, adds an extra impact near the place the first one hit.
- SOUL SHOCKWAVE (1 upgrade point): The impact now stuns the affected enemies for a brief duration.
- CALL OF THE DAMNED (3 upgrade points): After the impact, releases a bunch of spectres that chase and deal damage to enemies.
- EXTRA SPECTRES (2 upgrade points): Soul impacts now release additional spectres when they hit
- FEAR OF THE DAMNED (1 upgrade point): Enemies hit by the spectres decrease their movement speed for a few seconds.
- FEAST OF THE DAMNED (1 upgrade point): Each enemy killed by this spell reduces the cool down for the next cast.
- SOUL ECHOES (3 upgrade points): After the impact ends, there is a small chance of it striking again in the same place.
- TORNADO OF SOULS (5 upgrade points): When the spell is cast, extra impacts will fall across the battlefield.
