How do I get Alexandrite through Expert Roulette?

I heard you can obtain Alexdrandrite through Expert Duty Roulette, what is the quest call and where can I get this quest? After buying Ink and turn it in for Sphere Scroll, there is no more quest.

The first quest is in Hyrstmill. The actual quest giver is in Mor Dhona.

After you complete the Celestial Radiance quest (you need an Animus weapon for this, duh), you will have another quest at North Shroud near the atma/animus enchanter npc. The quest is called One Man's Trash. Tells you to go to Mor Dhona and talk to an old woman in the market. That same old woman npc will give you the daily quest you'll grab everyday "Morbid Motivation". This daily quest will ask you to do Expert roulette and will give a mysterious map as a reward when you deliver it. You descipher this map, find out which map/location it is and use Dig on the spot it marks, just like treasure hunting. A chest will appear and it will spawn mob(s) when you try to open it, giving you a guaranteed alexandrite when you kill all the enemies and open the chest. I would suggest you to not risk it and always make a party of at least 3~4 players for these maps so if you get a tough mob that has some powerful mechanics (like 5k damage bombs), you would have a better (guaranteed?) chance of succeeding. If you die, your map will be lost and you will lose your free daily alexandrite. You can still buy more of these maps for 800 myths each, or farm fates with an Animus weapon equipped with an atma-like drop rate (or even worse).

ps: edited for the post length.

Thanks for the helpful info Edeline, finally able to get the repeatable daily quest.