Assassin's Creed Mirage

First, make sure you have the Blowdart tool unlocked first.

Second, either find a guard with an orange key icon above their heads during a story mission (Like The Fiery Trail story mission) or a person dressed in black and carrying a Mysterious Shard. You would see them being escorted by two guards and they would casually walk together or stop at certain spots for a long period of time.

Third, in either scenario, knock either one out with a Blowdart tool, make sure they’re asleep, then either crouch or stand over them, hit to pickpocket them for the trophy to unlock. Quite simple, really!

PS: As a heads-up, I’m told by others that this trophy can be missable, so make sure you do a manual save first before trying it. Otherwise, you will miss out on it and will need to start over.

Have fun and good luck!

You'll need to unlock the Blowdart Tool and fully upgrade it to unlock Deep Slumber. Now, find a guard carrying a key item or mysterious shard and use the blowdart to put them to sleep. Then, sneak up and pickpocket them while they sleep.