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.- 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.
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 percent of the damage received to the attacker. Spiked Armor also affects Reinforcements and Heroes. (~12.5% reflection of 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 percent of the damage received 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 level)
- 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 level)
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.)
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.)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, spear throw is 24-40 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, spear throw is 24-40 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 (1-5 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 (1-5 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. (Physical damage is reduced by 10%)
- 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. (It doesn't when under area attack.)
Defensive Stance (1 Star): Barracks train soldiers with better armor. (Physical damage is reduced by 10%)
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. (It doesn't when under area attack.)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 (+4% 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 (+4% per tower beyond the first, to a maximum of +30%).Artillery
- Smoothbore (1 Star): Increases artillery attack range (by 10%).
- Alchemical Powder (1 Star): Artilleries 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 chance of stunning their targets on every attack.
Smoothbore (1 Star): Increases artillery attack range (by 10%).
Alchemical Powder (1 Star): Artilleries 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 chance of stunning their targets 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.
- Men-at-Arms (3 Stars): Men-at-Arms have more health and wear good armor.
- Champion (3 Stars): Champions have even more health and wield great weapons.
- Sworn Blades (3 Stars): Sworn Blades have the most health and wield dual weapons. (6-10 damage, Low armor)
- Recurve Bow (4 Stars): Gives reinforcements a ranged weapon that can target ground and flying enemies. (16-30 ranged damage)
Trained Volunteers (2 Stars): Trained Volunteers have additional health and deal a little more damage.
Men-at-Arms (3 Stars): Men-at-Arms have more health and wear good armor.
Champion (3 Stars): Champions have even more health and wield great weapons.
Sworn Blades (3 Stars): Sworn Blades have the most health and wield dual weapons. (6-10 damage, Low armor)
Recurve Bow (4 Stars): Gives reinforcements a ranged weapon that can target ground and flying enemies. (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 chance of causing heavy bleeding.
Barracks
- Elven Fencing (1 star): Reduces basic barracks construction costs. (-10% for level 1-3 melee towers)
- Expert Tactician (1 star): Increases barracks rally point range.
- Enchanted Armor (2 stars): Barracks equip soldiers with improved armor. (+10%)
- Moon Forged Blades (2 stars): Soldier attacks deal additional magic damage.
- Blessing of Elynie (3 stars): Soldiers have a chance of cheating death when dealt lethal damage.
Magic Tower
- Crystal Focus (1 star): Increases Mage attack range.
- Empowered Magic (1 star): Increases Mage attack damage.
- Crystal Gazing (2 stars): Increases Mage attack range (by 10%).
- Unstable Magic (2 stars): Mage attacks have a small chance (5%) of dealing triple damage. (It is shown as a "BLAST!".)
- Alter Reality (3 stars): Mage attacks have a chance of teleporting enemies back down the path.
Druid Tower
- Hardened Boulders (1 star): Increases Druid attack damage.
- 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.
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
- Elven Stars (3 stars): Gives reinforcements a ranged weapon that can target ground and flying enemies
- Green Wardens (3 stars): Green Wardens have more health, better armor and improved weapons.
- Rapid Response (3 stars): Reduces reinforcements cooldown by 5 seconds
- Moon Sentinels (4 stars): Moon sentinels are elite elven huntresses, riding giant panthers.
