Blue orbs (or spheres) can be obtained during gameplay or by spending real money. You need them in order to speed up the rituals and upgrades and also to buy exclusive items. 

There are several ways to get blue orbs:

1. Complete missions

Tap the thief icon on the right side of your dungeon to open the missions menu and see what missions you have. Completing missions will give you orbs and experience. When you complete a mission, a new one will appear in its place.

2. Level up 

You will receive orbs with each new level. To level up, collect green experience points scattered throughout the levels in both single and multiplayer modes.

3. Win leagues and guild battles
Take one of the top places when you finish your league or be one of the top contributors in Guild Battle to earn orbs. 

4. Lock picking
You will sometimes earn a few orbs while trying to open a dungeon door.

5. Visit the Store
Tap on the "+" icon next to orbs to buy more with real money. You can find out how to disable in-app purchases in the Billing section.