This achievement is gained upon defeating the following rare monsters found in the level 65+ hard difficulty adventures in The Rujarkian Hills: Arena of Chance:

Bloodied Harrower
Captive Coin Bank Robber
Captive Coin Bleeder
Captive Coin Sacrificer
Enslaved Mystic
Enslaved Prophet
Escaped Harrower
Famished Hound
Master Smith
Murdering Slave
Rabid Fleshfeaster
Rebellious Arcanist
Slave Marauder
Steelslave Beast Tamer
Steelslave Berserker
Steelslave Blademaster
Steelslave Emissary
Steelslave Infiltrator
Steelslave Priest
Steelslave Raid Chief
Steelslave Ravager
Steelslave Strategist
Steelslave Thrasher
Steelslave Trader
Steelslave Visionary
Steelslave War Criminal
Steeltusk Razorback