From The Heroes of Might and Magic III wiki

Class	Air Magic
Basic cost	7
Duration	1 round/Spell Power
Level	2nd

Reduces damage target allied creture takes from Air Magic spells.

Level	Effect
None	Damage reduced by 30%
Basic	Cost reduced by 2
Advanced	Damage reduced by 50%
Expert	Affects all allied creatures

[edit] Units capable of casting this spell

• Storm Elementals