Storm's Companion is a Unique Pants in Diablo IV Season 15. It drops from Andariel (Echo of Andariel).
Unique power
Your Wolf Companions are infused with the power of the storm, dealing [80-100%][x] increased Lightning damage and gaining the Storm Howl ability.
Affixes
1,500 Armor
+[1-3] to Wolves (1-3)
Where it drops
World drop (any difficulty, drop rate scales with Torment tier)
Dedicated drop: Andariel, Maiden of Anguish (Greater Lair Boss, Torment 1+; Boss Trophy: Pincushioned Doll)
Horadric Cube: Item Transmutation (Upgrade to Unique) - Common item of the same slot + 1 Enhanced Primordial Dust + 10 Primordial Dust (random Unique of that slot)
Horadric Cube: Item Transmutation (Amalgamation) - 5x Pincushioned Doll (Boss Trophy) rolls a Unique from this boss's pool; can roll Mythic quality with the 'Crafted' tag