Inside the Theater of Pain in Maldraxxus (not inside the dungeon) you'll find the Sword Sorrowbane stuck in the ground and
乌纳尔的手臂 attached to it. Both of them are clickable objects so try to grab them! Too weak? Then obviously you'll need to buff your strength!
Acquisition:- Do the prequests to unlock 奥·拉里纳's vendor option, buy a 异常力量药水 and keep it in your bags.
- Buy a 猩红之力 from 塔·特鲁 in Revendreth and keep it in your bags.
- Make sure World Quest 一路磕磕绊绊 is active and you have plenty of time to complete it.
- Buy a 传送卷轴:伤逝剧场 from 独眼的乔比 for 10 Gold or keep your 炉石 off cooldown and bind it to the Innkeeper close to Theater of Pain (maybe check the location of Sword & Arm inside the arena if you haven't seen it before)
- Complete 2x ballista repairs for the WQ without losing the first buff (10min real-time, so do not log out) to get 2x 坚韧不拔 (second stack will refresh timer).
- Head to Glutharn's Decay at far east of Maldraxxus.
- Click 4x 可食用的红伞菇s, then instantly use your 传送卷轴:伤逝剧场 or hearth back to Theater of Pain.
- Hurry up (80% slow) to get to 乌纳尔的手臂 within 2min (maybe you wanna use a 地精滑翔器工具包 on top of the stairs when using the Hearthstone).
- Use your 猩红之力 and 异常力量药水 now.
- Within 25sec click 乌纳尔的手臂 for 乌纳尔的手臂 and Sorrowbane to receive 哀伤克星 and 哀伤收割者 achievement. Congrats!
TomTom:
/way #1536 51.42 48.47 Oonar's Arm
/way #1525 53.14 41.31 Teleport Scroll Vendor
/way #1536 53.63 47.93 Unusual Strength Potion
/way #1536 37 47 Battle Hardened
/way #1536 76.44 56.72 Edible Redcaps
/way #1525 51.16 78.75 Strength of Blood Vendor
/way #1536 59.73 73.02 Explosive Strength Vial