Dust off that crouch button you never had to use in Valhalla, because the new Assassin's Creed Mirage is an honest-to-god stealth game, and a challenging one, at that. Guards aren't pushovers in combat and Basim can be downed by only a few hits, so it's best to play Mirage like an old Splinter Cell game: combat is a last-resort option, and you really should be sticking to the shadows.
To that end, I've prepared some tips that'll help you stay unseen, expand your toolkit, blend into the crowd, line your pockets, and enhance the authenticity of Mirage's absolute knockout of a setting.
Invest in more tools early on
Mirage places a much smaller emphasis on skill trees than the last few Assassin's Creed games. When it comes to expertly sneaking past guards, Basim's tools are the real star of the show, so I recommend focusing on unlocking more as your first priority. You're given one tool unlock for free, and I recommend grabbing the sleeping darts first. The rest are unlocked through the middle skill tree. It takes around six skill points to complete the set—throwing knives, smoke bombs, traps, blowdart, noisemakers—and it's a worthwhile investment before worrying about eagle or focus mode upgrades.
Visit general shops to buy outfit dyes
There are so many free ammo chests on the rooftops of Baghdad that I rarely had to visit general shops (represented by a bag icon on the map) to restock on tools, so it took me way too long to notice the other main thing these merchants sell: outfit dyes! You'll earn dyes for your default assassin garb through the main story, but other outfits have three alternate dyes that you'll find in shops and in treasure chests.
Sell your trinkets
It also took me too long to notice there's a second tab in stores to sell stuff. All those trinkets you've been looting from chests and pockets can and should be sold all at once for a big payout.
Don't sleep on sleep darts
This being a throwback Assassin's Creed, I expected to rely heavily on throwing knives to maintain stealth, but my favorite tool ended up being the basic sleep darts. They don't have the range or permanence of a throwing knife to the head, but they do have subtlety on their side. Putting a guard to sleep will "turn them off" for around 10 seconds. That's just long enough to sneak past their purview, and if another guard discovers their sleepy friend, they'll just wake them up instead of going on high alert (which makes stealth a lot tougher from there on). If you are out for blood, sleep darts are also a great backup if you're out of throwing knives. Their range can be upgraded after unlocking Tier 1, and a later upgrade even makes them lethal.
Smoke bombs are a combat cheat code
My second most-used tool after sleep darts were easily smoke bombs. These can be used to temporarily blind guards from a distance so you can pass unnoticed, but they're actually best used in combat. Throwing one at your feet (which you can do with the quick use command) in the middle of a fight will instantly incapacitate every guard around you, and susceptible to a hidden blade execution. This tactic is so overpowered that it almost feels broken—combat basically comes to a halt as Basim either makes an escape or kills everyone in the smoke cloud for free.
Merchants are the best option for infiltration
Most of Mirage's missions revolve around infiltrating a compound, and there are always multiple ways to do it. Study the exterior and you'll usually find a crumbly wall to exploit, but if there are merchants for hire outside the compound, consider paying for their services. I found merchants (as well as the rarer concubines faction) more useful than musicians and mercenaries because instead of just distracting guards, merchants will literally escort you behind enemy lines with a perfect cloak of social stealth. It feels cool every time and it's a lot more reliable than hoping a musician draws the attention of the one guard you're trying to bypass.
Faction Favor Tokens can be pickpocketed, if you're lucky
If you want to recruit merchants and mercenaries often, you'll need a lot of favor tokens. Side contracts are the best source of tokens, which you can pick up from any of the three assassins bureaus. The other way is to simply pickpocket merchants on the streets of Baghdad. I feel a little guilty every time I do it, because Basim really doesn't need the money, but sometimes citizens are carrying free favor tokens. Just be sure not to linger in one area too long—people will eventually notice you've pickpocketed them and call guards to their location.
Don't be afraid to let some guards see you
There are a few circumstances where letting a guard see you is actually a good idea. If you're trying to attract a single guard for a stealth kill and they're too far away to whistle, try revealing yourself and raising their suspicion just high enough to investigate your location (somewhere in the yellow phase of detection). The other time it'd be useful to break stealth is if you're out of tools and can't see a subtle route around a group of guards: as long as they're in an isolated area, entering combat with a few guards won't blow your cover for the rest of the compound. Just be aware that guards with a bell icon above their head will run straight to an alarm bell when alerted.
Consider playing in Arabic
This obviously has no gameplay advantage, but it sure made my playthrough more authentic and enjoyable. Mirage's Arabic cast is great—I particularly enjoy Lee Majdoub's more confident, stern take on Basim—and it's nice to have all the character voices match the background civilian dialogue which is all in Arabic anyway. You'll find the Arabic voice option in sound settings on consoles, but on PC you'll have to close Mirage and change its language setting within the Ubisoft Connect app.