Upgrading and Fusion

Upgrading
Aside from praying for luck at the carat shop, upgrading heroes is the other place where you will be praying for success.

Heroes can be powered up through a process called upgrading. To upgrade a hero, you must sacrifice another in order for a chance of successfully upgrading them. Upgraded heroes will be denoted by a +x at the end of their names where x is the number of times upgraded, up to a maximum of 5 times. Heroes must be fully upgraded (upgraded five times successfully) as well as fully leveled (level 30), before they can be used in fusion.

Upgrading is where the majorty of gold goes. Each upgrade costs gold, regardless of whether the attempt was successful or not, and if successful, subsequent upgrades cost more than previous ones. Additionally, heroes of higher rarity cost more to be upgraded, so you better keep your eyes out for leprechauns with pots of gold because you can run out quickly when upgrading higher rarity heroes.

Fusion
Unless you are extremely lucky all the time, fusion is the primary way of getting heroes of higher rarity.

Fusion is the process of combining two fully leveled, upgraded heroes of same rarity to form a new one. The process of fusion is always the same and will always form a new hero with a rarity 1★ higher than its fusion parents. Here are the rules and restrictions of fusion:
  1. Both heroes must be full leveled (level 30).
  2. Both heroes must be fully upgraded (+5).
  3. Both heroes must have the same rarity (3★ with 3★, 2★ with 2★).
  4. Fusions have a 100% change of success and never fail.
  5. Hero generated from fusion is always 1★ higher (fusing two 3★ produces one 4★).
Since fusion requires two level 30 +5 heroes, the majority of the time prepping for fusion is spent trying to upgrade. At higher rarities, getting 5 successful upgrades on a single hero can be quite hard, as it mostly comes down to luck.

Be sure to check the Tips on Upgrading and Fusion section!