"In the Inventor's Workshop you can research and upgrade your defensive fortification technologies. By upgrading the technology, you are able to strengthen your line of defense and protect your kingdom and its treasure."
The maximum level you can upgrade a structure is shown in the tables below. You can level up a construction for 3 or 4 times. Each time you upgrade a plan, you will allow to upgrade that at the Maximum Research Level listed near the column of plans. So if you want to upgrade an Arrow Tower to level 6, you have first to upgrade "Plan Arrow Tower level 2" that allow you to upgrade then it.
Maximum research levels
| Levels → | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Barricade | 1 | 2 | 2 | 2 | 3 | 3 | 3 | 4 | 4 | 4 | 4 | 4 |
| Arrow Tower | 1 | 1 | 2 | 2 | 2 | 2 | 3 | 3 | 4 | 4 | 4 | 4 |
| Spikes | 1 | 1 | 2 | 2 | 2 | 3 | 3 | 3 | 4 | 4 | 4 | |
| Bomb Tower | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 4 | 4 | ||
| Frost Tower | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 4 | 4 | |||
| Blockade | 1 | 1 | 2 | 3 | 3 | 4 | 4 | 4 | ||||
| Gargoyle Tower | 1 | 1 | 2 | 2 | 3 | 4 | 4 | |||||
| Firebolt Tower | 1 | 1 | 2 | 3 | 4 | 4 | ||||||
| Snake Tower | 1 | 2 | 3 | 4 | 4 | |||||||
| Skull Tower | 1 | 3 | 4 | 4 | ||||||||
| Lightning Tower | 3 | 3 | ||||||||||
| Jester Box | 2 | |||||||||||
| Heal Tower | 3 | |||||||||||
Levels
| Level | Requirement | Upgrade Cost | Upgrade Time |
|---|---|---|---|
| 1 | Throne Room level 1 |  1K
|
Template:Icon time 2m |
| 2 | 3K
|
Template:Icon time 10m | |
| 3 | Throne Room level 2 | 10K
|
Template:Icon time 30m |
| 4 | Throne Room level 3 | 25K
|
Template:Icon time 1h |
| 5 | Throne Room level 4 | 50K
|
Template:Icon time 4h |
| 6 | Throne Room level 5 | 100K
|
Template:Icon time 12h |
| 7 | Throne Room level 6 | 250K
|
Template:Icon time 1d |
| 8 | Throne Room level 7 | 500K
|
Template:Icon time 2d |
| 9 | Throne Room level 8 | 1M
|
Template:Icon time 3d |
| 10 | Throne Room level 9 | 2M
|
Template:Icon time 4d |
| 11 | Throne Room level 10 | 6M
|
Template:Icon time 5d |
| 12 | Throne Room level 11 | 8M
|
Template:Icon time 6d |
Plan Barricade
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 1 | |
| 2 | 6 | 25K
|
Template:Icon time 3h | |
| 3 | 9 | 150K
|
Template:Icon time 1d | |
| 4 | 19 | 350K
|
Template:Icon time 2d | |
Plan Arrow Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 1 | |
| 2 | 6 | 50K
|
Template:Icon time 4h 30min | |
| 3 | 9 | 250K
|
Template:Icon time 1d 12h | |
| 4 | 18 | 750K
|
Template:Icon time 3d | |
Plan Spikes
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
| 1 | 3 | Unlock Inventor's Workshop level 2 | ||
| 2 | 6 | 50K
|
Template:Icon time 4h 30min | |
| 3 | 9 | 250K
|
Template:Icon time 1d 12h | |
| 4 | 19 | 750K
|
Template:Icon time | |
Plan Bomb Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 3 | |
| 2 | 6 | 150K
|
Template:Icon time 4h 30min | |
| 3 | 9 | 750K
|
Template:Icon time 1d 12h | |
| 4 | 18 | 1M
|
Template:Icon time 3d | |
Plan Frost Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 4 | |
| 2 | 6 | 250K
|
Template:Icon time 4h 30min | |
| 3 | 9 | 750K
|
Template:Icon time 1d 12h | |
| 4 | 18 | 1.25M
|
Template:Icon time 3d | |
Plan Blockade
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 5 | |
| 2 | 6 | 150K
|
Template:Icon time 4h 30min | |
| 3 | 9 | 750K
|
Template:Icon time 1d 12h | |
| 4 | 18 | 1.5M
|
Template:Icon time 3d | |
Plan Gargoyle Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 6 | |
| 2 | 6 | 1M
|
Template:Icon time 1d 18h | |
| 3 | 10 | 2M
|
Template:Icon time 3d 12h | |
| 4 | 16 | 3M
|
Template:Icon time | |
Plan Firebolt Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 7 | |
| 2 | 6 | 2M
|
Template:Icon time 2d 6h | |
| 3 | 10 | 3.5M
|
Template:Icon time 4d 12h | |
| 4 | 16 | 5M
|
Template:Icon time 5d | |
Plan Snake Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 8 | |
| 2 | 6 | 1M
|
Template:Icon time 2d | |
| 3 | 10 | 2.5M
|
Template:Icon time 3d | |
| 4 | 16 | 3.5M
|
Template:Icon time 4d | |
Plan Skull Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 9 | |
| 2 | 6 | 3M
|
Template:Icon time 2d 6h | |
| 3 | 9 | 4M
|
Template:Icon time 3d 9h | |
| 4 | 15 | 5M
|
Template:Icon time 4d 12h | |
Plan Lightning Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time | |
|---|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 10 | ||
| 2 | 6 | 4M
|
Template:Icon time 2d 6h | ||
| 3 | 9 | 5M
|
Template:Icon time 4d 12h | ||
Plan Jester Box
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 12 | |
| 2 | 6 | 4M
|
Template:Icon time 2d | |
Plan Heal Tower
| Picture | Level | Max. Research Level | Upgrade Cost | Upgrade Time |
|---|---|---|---|---|
 |
1 | 3 | Unlock Inventor's Workshop level 12 | |
| 2 | 6 | 4M
|
Template:Icon time 2d 6h | |
| 3 | 9 | 5M
|
Template:Icon time 4d 12h | |