Assassin's Creed Mirage is one of those games you can finish in under a week, but there are quests that can be hard to complete especially if the instructions don't lead you to the exact location and objective. One of them is finding Nehal's hidden place. It's not that hard to find if you have the right clues.
Location in the Map
If you've already found the clues that lead to the location, then you already know that it's in an oasis and that it's north of Aqarquf Dunes. Even if you haven't explored the portion of the map where the location is, the oasis is quite visible.
You can find it just east of Anbar, and if you're already synchronized with the fast travel point in Basim's hometown, then you'll be closer to it. Just mark the oasis then ride toward the mark until you see water.
Try to synchronize with the fast travel point there as well since you will be returning to that spot at least two more times. If you already have enough shards from assassinating Order of the Ancients members, then you won't really have to.
Where is the Entrance?
If you try to look for the entrance in and around the infrastructure where you synchronize, you're looking at the wrong place. The entrance is actually underwater, so you need to dive into the oasis to find it below.
It's a bit far before you can resurface in an underwater cave, but it will only take up around 50% of Basim's capacity to hold his breath. You have to swim way down before you see the entrance which will be obvious since it's the only part that sinks further.
Once you're there, you'll notice that the walls are of Isu architecture, meaning that you can expect to find objects such as Isu weapons, which you will. You'll just have to jump and run to the location, where you'll find three items.
What Do You Get?
There are two weapons, which are a dagger and a sword, and one armor you can unlock. You'll be needing shards to unlock them since they are protected by some kind of force field. Some need more than others, so you better start collecting them.
For the dagger, you only need two mysterious shards, which you might already have right away if you do the quest a little later. You will need three shards for the sword, and finally, five shards for the Milad armor. All in all, you can go around and collect ten shards before you do the quest.
When Should You Get It?
If you haven't found weapons that fit your fighting style, then you can go for the Isu set. The Milad armor allows you to set off a blinding flash after an air assassination, allowing you to escape before you are detected.
The sword will increase your damage by 50%. However, it will also reduce your maximum health by 50%. The dagger is good for health regeneration since it heals 10% of Basim's health for every five hits.
