Heroes need to upgrade their levels:
advanced stones, gold coins, experience points.
Source of gold coins:
Challenge Bosses, receive gold coins, fast raid, gold coins trial, daily tasks, on-hook earnings, voyages bounty, etc.
Source of experience points:
Challenge Bosses, fast raid, on-hook earnings, experiences trial.
Source of advanced stone:
Hero Sacrifice in the Hall of Ascension, fast raid, daily quest of emerald tower, advanced stone and gold coin trial
