From The Heroes of Might and Magic III wiki

Increases the amount of Melee damage done by the units under your hero's command:

Level	damage %
None	100%
Basic	110%
Advanced	120%
Expert	130%

Recommended for: Any Hero who can afford the extra slot

[edit] Heroes that specialize in Offense

• Crag Hack the Barbarian
• Gundula the Battle Mage