Chainscourged Mail is a Unique Pants in Diablo IV Season 15. It drops from The Butcher.
Unique power
Casting a damaging Brawling Skill disables it afterwards. When all of these Skills that are on your Action Bar are disabled, they become re-enabled with their Cooldowns refreshed. Brawling Skills you Cast deal [80.0 - 100.0]%[x] increased damage for each disabled Skill.
Affixes
Strength
+Ranks to Brawling Skills (1 - 2)
Where it drops
The Butcher (Lair Boss hoard - targeted drop)
Any Lair Boss general unique pool / world drop at Torment (chance rises per Torment tier)
Horadric Cube: Item Transmutation - Upgrade to Unique (Common base of same type + 1 Enhanced Primordial Dust + 10 Primordial Dust) rolls a random unique of that item category