Protective fire is the preferred tactic of your siege engines during defense. After hundreds of battles, your warriors have mastered it perfectly. Upgrading this Knowledge increases the offense of your siege engines during defense.
| Level | Gold | Soul Shard | Time | Requirements | Siege Offense During Defense | Influence | Hero’s Experience |
| 1 | 105K | 21K | 41w 3d 00h 00m 00s | Siege offense against ranged 1, Oracle 36 | 1% | 13K | 34K |
| 2 | 160K | 31.5K | 61w 3d 00h 00m 00s> 1 Year(s) | Siege offense against ranged 2, Oracle 36 | 4% | 29K | 42.5K |
| 3 | 220K | 46.5K | 91w 1d 00h 00m 00s> 1 Year(s) | Siege offense against ranged 3, Oracle 36 | 8% | 65.5K | 53K |
| 4 | 275K | 68.5K | 135w 2d 00h 00m 00s> 2 Year(s) | Siege offense against ranged 4, Oracle 37 | 13% | 150K | 66K |
| 5 | 330K | 105K | 200w 6d 00h 00m 00s> 3 Year(s) | Siege offense against ranged 5, Oracle 37 | 18% | 335K | 82.5K |
| 6 | 385K | 155K | 298w 2d 00h 00m 00s> 5 Year(s) | Siege offense against ranged 6, Oracle 37 | 25% | 750K | 105K |
| 7 | 450K | 225K | 63w 2d 00h 00m 00s> 1 Year(s) | Siege offense against ranged 7, Oracle 37 | 34% | 1.7M | 130K |
| 8 | 545K | 335K | 657w 6d 00h 00m 00s> 12 Year(s) | Siege offense against ranged 8, Oracle 38 | 45% | 3.85M | 160K |
| 9 | 720K | 495K | 976w 6d 00h 00m 00s> 18 Year(s) | Siege offense against ranged 9, Oracle 38 | 58% | 8.65M | 195K |
| 10 | 1.1M | 735K | 1 450w 4d 00h 00m 00s> 27 Year(s) | Siege offense against ranged 10, Oracle 38 | 75% | 19.5M | 240K |
| 4.29M | 2.22M | 3 977w 00h 00m 00s> 76 Year(s) | 75% | 35.04M | 1.11M |
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