Ressources

Crystals
Can be used to buy things in the shop and to upgrade orbs. They can be obtained by completing quests, logging in, defeating devils, spinning the lucky wheel, selling orbs or getting rewards from the tavern brawl.

Potions
Can be used to train your heroes without actually fighting. They can be obtained by completing quests, logging in, defeating devils, spinning the lucky wheel or buying them in the shop.

Devil Token
Can be used to get more heroes. There are small, medium and large token. Small token can result in 1-3 star heroes, medium token can result in 3-5 star heroes and large token can result in 4-5 star heroes. They can be obtained by completing quests, logging in, defeating devils, spinning the lucky wheel, buying them in the shop or getting rewards from the tavern brawl.

Evolution Coins
Can be used to change the skills your heroes use. They can be obtained by logging in or defeating one of the two bosses. Below a table with the costs for changing a skill. There are currently no 3 star heroes with more than their default skills.

Devil Shards
Can be used to get more heroes. There are medium, large and choice shards. For a medium devil you need 50 shards, for a large devil 100 shards and for a hero of your choosing (only 5 star I think) 100 choice shards. They can be obtained by defeating devils or logging in.

Heroes
Can be used to upgrade other heroes and are your fighting power. They can be obtained by exorcising devils. Training of heroes goes up to "6 stars" where the 5 stars turn orange. Heroes can only be trained to a certain level depending on their star. Luckily once they hit the level cap of their current star they can be upgraded to the next star. For that you need to go to the barracks and push the "Evolve" button. You are then asked to click on a number of heroes that have the same star level to sacrifice them for the evolution. The number you need is equal to the number of stars the hero currently has.

Types of Heroes
There are three types of heroes: During a fight you can see how they interact with each other in the upper right corner. Attacking with a type advantage means you deal 20% more damage while attacking with a type disadvantage can result in glancing hits with a 50% chance which deal 50% less damage and have a 50% chance not to inflict the status they normally would.
 * yellow - Tank, advantage against blue
 * red - mage, advantage against yellow
 * blue - weapon damage dealer (not sure what to call it), advantage against red

Skills
Every hero has 3 skills they can use (except Cailien which has 4 for some reason). There are active and passive skills. Active skills are, as the name suggests, skills that you can activate during the fight while passive skills are in effect as long as the hero is alive. Who would have guessed, right? Each active skill also has a cooldown before it can be used again. Some heroes have more than their default skills. You can change their skills for the cost of evolution coins. For more info on skills see each heroes respective page(Category:Hero) or the combat page.

Keys
Can be used to fight one of the bosses. They can be obtained by defeating the other of the two bosses, the Key-Guardian.

Orbs
Can be equipped to your heroes to increase their stats. They can be obtained by logging in, defeating devils or spinning the lucky wheel. There are 4 types of orbs as well as 5 different levels and they can be upgraded 15 times each. In the table below are the +15 primary stats for the different level and types of orbs: Additional to the primary stat each orb can have up to 4 secondary stats or none at all. Orbs can also be enchanted and get one enchantment for every 3 upgrade level.

Below the upgrade chances for each upgrade: