This pack contains 5 pets:

Jojo - Passively boosts gold drops.
Ermea - Passively boosts fire rate / attack speed.
Karam - Passively boosts damage.
Gernondu - Collects loot in radius.
Numuo - Passively boosts movement speed.

All 5 of them are passive pets and tier 1. You can upgrade all pets' tiers in game. You can't upgrade a tier of a pet if you don't own the pet.