Upgrades follow a more traditional level-up system, with the max level for a hero dependent on the level of your Headquarters at the time. Tiers, meanwhile, require special items called Hero Shards, and each tier increase gives a substantial buff to HP, attack and defence. Take note of how many Shards you have for each rarity and hero, and if you can promote someone to the next tier, do it immediately. Upgrades follow a more traditional level-up system, with the max level for a hero dependent on the level of your Headquarters at the time. Tiers, meanwhile, require special items called Hero Shards, and each tier increase gives a substantial buff to HP, attack and defence. Take note of how many Shards you have for each rarity and hero, and if you can promote someone to the next tier, do it immediately.