In Mu Blue from Season 5 Episode 4 the Inventory Items option is added, which depending on the item can reinforce the damage, HP, SD, MP, and are purchased through the Mu Item Shop.

Inventory Item Features

SCULPT: Increases the character's attack powers.
CHARM: Increases the Status of the Character.
ARTIFACTS: Increase the configuration characteristics of the server.

Kind	Name	characteristics	Image
SCULPT	Figurine of Hawk	Increase Critical Damage + 10%
	Figurine of Antelope	Increase Excellent Damage + 10%
CHARM	Oak Charm	Increase HP +50
	Golden Oak Charm	Increase HP +100 & SD +500
ARTIFACTS	Worn Horseshoe	Increase Drop Rate by + 20%

NOTE: Items of the same type cannot be used at the same time.
 

Example:
Statue of Hawk + Statue of Goral = not working
Statue of Hawk + Golden Oak Charm = yes they work

How to use
To be able to activate or deactivate the inventory items you have to right click on the item.