Mark of the Assassin - Act 2 Side Quest
Location: Aman'lu and Upper Mines of Kaderak
Closest Portal: Upper Mines of Kaderak (West)
Objective: Obtain the Dwarven Mythril Ring and give it to Valeria in Kalrathia. Then defeat the Assassin in Kalrathia
Reward: Giethaa and Citaa Dual Wield Set Weapons; Other Gold + Loot too
Mark of the Assassin is a Side Quest which begins in Act 2 by picking up a Liantir Stone on a desk in the town of Aman'lu. After picking up this stone an Assassin will attack your character and knock you unconscious after which Danadel, an elf, will talk to you and explain what happened.
For the next step of this quest you will need to speak with Valeria in Kalrathia (Act 3) and update your task here. You can find Valeria inside of the Kalrathia Magic Shop, a location you'll be visiting a lot throughout Act 3. Valeria asks you to venture into the Upper Mines of Kaderak where you'll need to obtain a Dwarven Mythril Ring for her.
You'll find the Dwarven Mythril Ring around the entrance area of the Upper Mines of Kaderak. There will be a lever which you must pull that will uncover the hidden door that leads to the room with the ring; thankfully the lever is out in the open and easy enough to spot. If you need additional help finding this location check my screenshot below.
With the Dwarven Mythril Ring in hand return to Valeria in Kalrathia and speak with her to update your quest. She'll drop a Dwarven Mythril Ring of Sight on the ground which you'll need to equip on one of your characters for the next part of this quest. Head over to Merchant Kendril who is staying in the Kalrathia Inn and when you speak with him a scene will occur with the Assassin showing up.
Defeat the Assassin and he'll drop twin blades for you which are set items; they make great weapons for any Dual Wield characters you have (like Eva). Speak with Merchant Kendril to complete the quest and to receive an additional smaller reward.