Souls

Souls are things Yokai will drop, thought there's a high chance they'll drop them. It is not guaranteed a foe will drop Souls

If you wanted to Describe Souls, They could be Described as special abilities.

You have a Wheel, The Wheel is what you use to contain Souls though, be warned, they can each only be used once. Your Wheel can contain up to 7 regular Souls. Certain special souls take up 2/7 and are permanent. They can be reused but you have to wait for them to recharge. You get them after completing Levels.

Appearance
Souls usually look like 3d drawings in Orbs.

Gameplay
Souls will usually grant the player affects or attack to help the player in battle.