In Blades of Brim we have three kinds of Pets Rarity: Common, Rare, and Epic. Rarity determines the Summon Duration - when the Pet is active after being summoned.   

Summon Duration can be upgraded with Coins. 

Pets can be unlocked in the ‘‘Me’’ menu. You will gain access to new Pets by leveling up. Some Pets are buyable in the Shop. You can also find Pets in Chests. 

Common Pets can be found in Common Chests, Rare Pets can be found in Rare Chests, and Epic Pets can be found in Epic Chests.