As your heroes level up, they'll be able to use higher tier gear! The level requirements for each tier are below.

Tier 2: Level 3
Tier 3: Level 6
Tier 4: Level 9
Tier 5: Level 12
Tier 6: Level 16
Tier 7: Level 19
Tier 8: Level 22
Tier 9: Level 26
Tier 10: Level 29
Tier 11: Level 32