From The Heroes of Might and Magic III wiki
|Basic Armorer: reduces all damage inflicted against the hero's troops by 5%.|
|Advanced Armorer: reduces all damage inflicted against the hero's troops by 10%.|
|Expert Armorer: reduces all damage inflicted against the hero's troops by 15%.|
Armorer is a secondary skill, that reduces the physical damage done to hero's creatures. Physical damage means damage done by enemy creatures engaged in melee or ranged combat. Armorer secondary skill does not reduce damage from spells cast by enemy heroes or creatures.
Heroes who specialize in armorer skill:
It should be noted, that due to a bug in the game, the damage from arrow towers during siege combat is not reduced by armorer secondary skill, but actually increased the corresponding amount.
Armorer skill is unquestionably one of the most useful secondary skills in the game. At expert level it reduces 15% of all physical damage, which, though not strictly speaking true, effectively increases allied creatures' health by 15%. This on the other hand leads to less casualties in battles, and more troops for the next battle. Escpesially in extra large maps this may give the needed edge to vanquish the enemy.