This item drops from world boss Nurgash Muckformed in Revendreth. It can be runecarved into pants or a back piece.

Hi all

You can find him in Revendreth 27 14. He is using 2 AoE hits.
1st is on front of tank 大地冲击
2nd is around him 巨石雹 Stay close to him.
Extra hit for tanks 石拳
As well He can get sleep and don't care about you xD 深度沉睡

See My Video if need it - https://youtu.be/3JHfgyse1jA

His drop:

罪碑肩垫
舒适的午睡裹腕
诺尔伽什的万千罪碑腰带
叮当响的踏石靴
硬化的碎堡手套
泥躯锁链项圈
狂热畸兽的回忆
古怪的邪能核心的回忆
阿兹亚基的疯狂的回忆

Hope that help You :).

Doesn't it drop from torgast layer 6 or higher too like icy-veins says?

小知识

屏幕截图

视频

狂热畸兽的回忆

物品等级：1
拾取后绑定
唯一

掉落于: 诺尔伽什·泥躯

符文铭刻之力

黑暗突变还会使你与你畸兽的攻击速度与伤害提高12%。

指南