As Cobra Amulet has significant role in Tibia's lore, Adding to Zupakode Answer:
Lionet's answer about Lore of the Cobra Amulet - https://www.tibia.com/forum/?action=thread&postid=38769695#post38769695:
"I really appreciate the interest of the Tibia Community in our lore and stories! Here are some additional notes on my story of Scarlett and Galthen:
The Cobra amulet is an extremely powerful artifact with an unknown origin as of now. Its traits are concentrated on a single individual but the curse will affect all things directly connected to the amulet and its wearer. When the amulet is returned to its eternal resting place, everything the taker, thus owner, of the amulet has experienced from that point in time onward will be undone. All of this, as already mentioned, will only affect events in direct relation to the bearer of the amulet and the bearer him- or herself.
In the case of Scarlett and Galthen, Scarlett was blinded towards Galthen while in turn a successful search for Scarlett was impeded by the amulet. Returning it to its resting place will alter the timeline for Scarlett (and also Galthen who is directly connected to the Scarlett, the amulet and ultimately the curse). So in their world, the events after the crypt never took place. Everything before that will still have happened. However, without the power of the Cobra, Scarlett will not continue the assassin path much further and she, as well as Galthen, will have the possibility to find each other. Both their searches would eventually be successful as they belong together.
By chosing to return the amulet, players are effectively building a somewhat happy ending for the two but will lose the amulet. That is why the note says: "You are truly selfless"."