In Arena of Valor, Arcanas is one of the most important extra assist item for each heroes and can be found inside the shop, there are 8 types of Arcanas and divided into 3 tiers.

 Arcanas Vault

Arcanas Vault

This is where the all the arcanas gose in and give you all the extra attackdamage,hp,ability damage,defense,life steal,attack speed,critical chance and piercing. 
Each Arcanas slot will be unlock for player when they gain up a level.
Arcanas slot are all unlock on level 30.

Arcana types:

Knowing Arcanas info that will fit player play style and hero is important before buying an Arcanas.

This is the list of all Arcanas from Tier I to Tier III.

Tier I Arcanas 

Tier II Arcanas

Tier III Arcanas