The Tower Modules: Rarities, Merging, Sub-Effects and Unique Effects

How modules work

Modules unlock at the Tier 2 Wave 90 milestone. You equip one module of each type, and each type feeds a different part of your tower.

• Cannon Attack

  Main effect raises tower damage. Sub-effects roll attack workshop stats such as attack speed, crit, range, multishot, bounce shot and rend armor.

  • Unique effects: 7
  • Sub-effects: 17
• Armor Defense

  Main effect raises tower health. Sub-effects roll defense stats such as regen, defense, thorns, orbs, shockwave, land mines, death defy and wall stats.

  • Unique effects: 7
  • Sub-effects: 17
• Generator Utility

  Main effect raises your coin bonus. Sub-effects roll utility stats such as cash, coins, free upgrades, interest, recovery packages and enemy level skips.

  • Unique effects: 6
  • Sub-effects: 13
• Core Ultimate Weapons

  Main effect raises Ultimate Weapon damage. Sub-effects roll stats for individual weapons, so only the ones for weapons you use matter.

  • Unique effects: 6
  • Sub-effects: 26

Every module has up to three kinds of stats. The main effect is the only one that grows when you level the module. Sub-effects are random rolls you can reroll with reroll shards. A unique effect exists only on modules that were pulled as epics.

Getting modules: pulls, drops and shards

You get 10 free module tickets when the system unlocks. After that, pulls cost 20 gems each or 200 gems for ten. The Standard Banner is always available, and a featured banner with shifted epic odds sometimes runs next to it. Each banner shows its own epic distribution in game.

Common

68.5%

Rare

29%

Epic

2.5%

Pity epic

150 pulls 3,000 gems at worst

At 2.5% an epic takes 40 pulls on average, which is 800 gems. Bad luck protection guarantees one after 150 pulls without an epic, and every ten-pull contains at least one rare. Epics pulled this way are called natural epics, and they are the only modules with unique effects. A module you already own at 5-star Ancestral becomes less likely to be pulled.

Boss drops

Bosses can drop common modules (2% base chance), rare modules (0.5% base chance) and reroll shards (15% chance). The Common Drop Chance and Rare Drop Chance labs each add up to 1%. Only commons and rares drop this way.

Module shards

Leveling a module costs module shards and coins. Shards come from daily missions, the event shop, the guild store, and from shattering modules you do not need: 5 shards per common and 10 per rare. A merged module shatters for the combined value of everything merged into it. Natural epics can only be shattered once you have built a 5-star Ancestral of that same module.

Rarity ladder and merging

Merging raises a module to the next rarity. That lifts its level cap, improves the main effect and its scaling, opens more sub-effect slots, and on natural epics strengthens the unique effect. How far a module can go depends on how it started.

• Common modules cannot be merged. They are merge material and shard fodder.
• Rare modules can be merged up to Legendary+. They keep their original name and never gain a unique effect, even at Epic or above.
• Epic modules (natural epics) can be merged all the way to Ancestral, then starred up to 5 stars.

Slots are worked out from the level thresholds 41, 101, 141, 161, 201 and 241. The wiki rarity table still shows 6 slots for starred Ancestral modules, while its text lists the 201 and 241 unlocks.

The merge screen shows two kinds of ingredients. A module icon means a copy of the exact same module at the rarity shown. A wildcard icon means any module of the same type at that rarity, which is where merged rares earn their keep. The first module you tap is the one being upgraded.

A full 5-star Ancestral takes 18 copies of the same natural epic in total: 8 to reach Ancestral and two more per star. Each star raises the level cap by 20 and boosts the main effect.

The Unmerge Module lab (Tier 8 Wave 20) lets you undo a merge. If the merge used a duplicate natural epic, you get the lower-rarity module and the epic back. If it used wildcards, the wildcard material comes back as shards.

Leveling and shard costs

Levels raise the main effect and unlock sub-effect slots. A module starts with two slots and gains one at each of levels 41, 101, 141, 161, 201 and 241. Since level caps come from rarity, a slot can be out of reach until you merge.

Base costs before the Module Shard Cost and Module Coin Cost labs, which each cut up to 30%. The wiki only lists these checkpoint levels.

The restore button refunds every shard and coin spent on a module at no charge. Sub-effects stay as they are, including ones in slots that need a higher level, and spent reroll shards are not returned. That makes it safe to move levels between modules when you swap builds.

Sub-effects and rerolling

Each sub-effect slot holds one random effect from the pool for that module type, at a random rarity. Sub-effect rarity is rolled separately from the module, but it is capped at the module's current rarity. A Legendary module can show a Common sub-effect and can roll up to Legendary, never Mythic.

Rerolling costs reroll shards and rerolls every unlocked slot that is not locked. Locking keeps the effects you like but makes each reroll far more expensive, so the last slot on a module costs the most to finish.

The wiki marks the 6-lock and 7-lock costs with an asterisk and does not explain it.

Auto Roll rerolls quickly until it lands on an effect and rarity you marked as acceptable, and you can cancel it at any point. The effect ban labs remove chosen effects from the pool. Some core effects ban themselves for free once they can no longer help: Spotlight angle at 90 degrees, and Chrono Field duration or cooldown once maxed.

Reroll shards from bosses

When a boss drop triggers (15% chance), the amount depends on the tier you are playing. The Reroll Shards lab adds up to 100 more per drop.

Cannon sub-effects

Armor sub-effects

Generator sub-effects

Core sub-effects

A dash means the effect cannot roll at that rarity. Core effects only do anything if you own the matching Ultimate Weapon.

Enemy Attack Level Skip and Enemy Health Level Skip on generators can be modeled with the enemy level skip calculator before you spend reroll shards chasing them.

Epic module unique effects

There are 26 natural epics, and each carries one unique effect that gets stronger at Legendary, Mythic and Ancestral. These are the reason to pull modules at all: several of them change how a whole system behaves instead of adding a number.

Cannon

Amplifying Strike also boosts Ultimate Weapon damage, and a new boss or elite kill refreshes its timer.

Armor

Space Displacer mines use your own Inner Land Mines stats if you own the weapon, otherwise the level 1 multiplier. Sentry Protocol fires faster with more orb speed.

Generator

Pulsar Harvester has diminishing returns after 100 level reductions on an enemy and a hard cap of 400. Restorative Bonus refreshes on a new package and does not stack.

Core

Multiverse Nexus adds 20 seconds at Epic and subtracts 10 at Ancestral. Dimension Core stacks additively: with the shock multiplier lab maxed, 20 stacks reach a 27.4x total multiplier.

• Project Funding never drops below a x1.00 multiplier.
• Black Hole Digestor counts a free upgrade trigger even when every upgrade in that category is already maxed.
• Anti-Cube Portal and Negative Mass Projector still count enemies as hit when those enemies are immune to the shockwave or orb itself.
• Space Displacer mines deal no damage in an Ultimate Weapon Dissonance run. See the Dissonance Run planner for how those runs work.

Two of these have their own reference pages here: the Pulsar Harvester curve shows how its level reductions fall off, and the bot coverage calculator is the place to check what extra bot range, such as Singularity Harness adds, does to your coverage.

Assist modules

Assist modules arrive at the Tier 19 Wave 40 milestone. For 1,000 stones per slot you can equip a second module alongside the main one. It contributes a weaker copy of its unique effect, main effect and sub-effects. You cannot assist with a module that has the same name as the main one, and the assist module has its own level, so it needs shards of its own to unlock more than two sub-effects.

• Unique effect rarity: starts at Epic on unlock. Upgrading to Legendary, Mythic and Ancestral costs 1,000, 1,200 and 1,400 stones, for 4,600 stones including the unlock.
• Main effect efficiency: starts at 1% and can be bought up to 100% for 16,038 stones.
• Sub-effect efficiency: starts at 1% and can be bought up to 70% for 8,073 stones.
• Labs: two labs unlocked at Tier 19 Wave 50 raise main effect and sub-effect efficiency by 1% per level over 30 levels.

Each step costs 3 stones more than the one before, starting at 15 stones for 2%. Totals are summed from the per-level costs.

Fully buying out one assist slot with stones costs 4,600 + 16,038 + 8,073 = 28,711 stones, and each module type has its own slot. Those stones compete directly with Ultimate Weapon upgrades.

Assist bonuses do not break hard caps. The wiki lists 98% defense, 90% Chrono Field slow, 150 seconds off wall rebuild, 7 seconds shockwave frequency, 50% Death Defy and a 37 second Inner Land Mines cooldown as limits that still apply. Since v27.1 the assist main effect multiplies with the main module for all four types.

Module labs

Module labs open in three waves: drops and shards at Tier 4, cost reductions and effect bans at Tier 10, and assist efficiency at Tier 19. Module Shard Cost is the one with the widest effect, because it discounts every level on every module you will ever raise.

Times are base research times before lab speed bonuses.

Core Effect Bans has the most levels because the core pool is the largest and most of it is tied to weapons you may not use. Banning the effects of weapons you do not run makes every core reroll more likely to land on something useful.

Frequently asked questions

How do you unlock modules in The Tower?

Reach Tier 2 Wave 90. You get 10 free module tickets, and after that each pull costs 20 gems, or 200 gems for ten.

What are the module pull rates?

On the Standard Banner a pull is 68.5% common, 29% rare and 2.5% epic. You are guaranteed an epic after 150 pulls without one, and every ten-pull includes at least one rare.

Can a rare module get a unique effect?

No. Only modules pulled as epics have unique effects. A rare can be merged up to Legendary+ but keeps its name and never gains one.

How many epic copies do you need for a 5-star Ancestral module?

18 copies of the same natural epic in total: 8 to reach Ancestral and two more for each of the five stars. That raises the level cap to 300.

What are the chances of an Ancestral sub-effect?

Each rolled slot has a 0.3% chance of Ancestral, 1.0% Mythic, 2.5% Legendary, 10% Epic, 40% Rare and 46.2% Common. The module must be Ancestral itself to roll an Ancestral effect.

How much does it cost to reroll module sub-effects?

A reroll with nothing locked costs 10 reroll shards. Locking slots raises it to 40, 160, 500, 1,000 and 1,600 shards for one to five locks.

Sources and credits

The numbers on this page come from the community-maintained The Tower - Idle Tower Defense Wiki and were reorganized and rewritten for Towerstats.org. Wiki text is available under CC BY-SA.

• Modules
• Modules/Merging
• Modules/Cost
• Sub-Module Effects
• Epic Module Unique Effect
• Module Labs
• Module Labs/Common Drop Chance
• Module Labs/Reroll Shards
• Module Labs/Daily Mission Shards
• Module Labs/Unmerge Module
• Module Labs/Module Shard Cost
• Module Labs/Module Coin Cost
• Module Labs/Rare Drop Chance
• Module Labs/Cannon Effect Bans
• Module Labs/Armor Effect Bans
• Module Labs/Generator Effect Bans
• Module Labs/Core Effect Bans
• Lab/Shatter Shards
• Assist Module Labs
• Lab Category/Module Research