Combat units in the underworld can be upgraded in two ways so they can take on higher-level heroes.

1. By upgrading the goblin pit, troll block and keeper. The respective units get stronger through fellow units or better equipment.
2. By upgrading the units in the upper area of the underworld. Click the "+" button to upgrade their levels and attributes.

The maximum level of units is 600. They have the warrior class and differ in their luck attribute.

Graphic	Name	Function	Attribute Factor
	Goblin	First line of defense	0.192
	Troll	Second line of defense	0.215
	Keeper	Last line of defense	0.43