Every fight, every skirmish, every battle for a Fortress leaves scars on a Viking's body. But this makes the Viking even stronger and more resilient. Upgrading this Knowledge increases your army's health in battles for Fortresses.
| Level | Gold | Soul Shard | Time | Requirements | Troop health in Fortresses | Influence | Hero’s Experience |
| 1 | 105K | 21K | 41w 1d 00h 00m 00s | Troop Health When Guarding Fortresses I 1, Oracle 36 | 1% | 16K | 40K |
| 2 | 160K | 31K | 8w 5d 00h 00m 00s | Troop Health When Guarding Fortresses I 2, Oracle 36 | 2% | 35.5K | 50.5K |
| 3 | 215K | 46K | 90w 4d 00h 00m 00s> 1 Year(s) | Troop Health When Guarding Fortresses I 3, Oracle 36 | 4% | 80.5K | 64K |
| 4 | 270K | 68K | 134w 3d 00h 00m 00s> 2 Year(s) | Troop Health When Guarding Fortresses I 4, Oracle 37 | 6% | 185K | 80.5K |
| 5 | 325K | 105K | 199w 5d 00h 00m 00s> 3 Year(s) | Troop Health When Guarding Fortresses I 5, Oracle 37 | 8% | 410K | 105K |
| 6 | 380K | 150K | 296w 3d 00h 00m 00s> 5 Year(s) | Troop Health When Guarding Fortresses I 6, Oracle 37 | 11% | 925K | 130K |
| 7 | 445K | 225K | 440w 2d 00h 00m 00s> 8 Year(s) | Troop Health When Guarding Fortresses I 7, Oracle 37 | 15% | 2.1M | 160K |
| 8 | 540K | 330K | 653w 5d 00h 00m 00s> 12 Year(s) | Troop Health When Guarding Fortresses I 8, Oracle 38 | 19% | 4.75M | 195K |
| 9 | 710K | 490K | 970w 5d 00h 00m 00s> 18 Year(s) | Troop Health When Guarding Fortresses I 9, Oracle 38 | 24% | 11M | 240K |
| 10 | 1.1M | 730K | 1 441w 3d 00h 00m 00s> 27 Year(s) | Troop Health When Guarding Fortresses I 10, Oracle 38 | 30% | 24M | 295K |
| 4.25M | 2.2M | 4 277w 1d 00h 00m 00s> 81 Year(s) | 30% | 43.5M | 1.36M |
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