1. Collectibles
1.1. All Secrets (Godlike)
1.2. All Royal Letters (A Life in Letters)

2. Miscellaneous
2.1. Look Out Below – Kill three enemies with a single stack of hanging barrels
2.2. Queensbury Rules – Reach combo level 40
2.3. Opium Scourge – Affect four enemies simultaneously with Hallucinogenic Dart
2.4. Needle in a Haystack – Kill 5 enemies from within the same haystack
2.5. Artisan – Craft a Level 10 Item

Godlike
Unlock all of the Secrets of London.
There are 32 Secrets of London in Assassin’s Creed Syndicate. Finding all of their locations unlocks the Godlike trophy / achievement and the Aegis Outfit for Evie.
The secrets are music boxes that you must pick up. You can hear them when close enough. Use eagle vision to locate them quicker. Unlike other collectibles there isn’t a map available at merchants. You can buy a map from the E-Store with microtransactions, but this costs real money.

Once all London Secrets have been found you must bring them back to Reuge’s Vault. Interact with all levers in the vault and you will unlock the Aegis outfit and the Godlike trophy or achievement. You also receive 4 skill points.

A showcase of the Aegis outfit / armor can be seen at the end of the video. It’s the best outfit in the game and you should get it as early as possible. It can only be worn by Evie.

A Life in Letters
Collect all of the Royal Letters.
There are 12 Royal Correspondence Letters in Assassin’s Creed Syndicate. Finding all their locations unlocks the “A Life in Letters” trophy / achievement.
The merchants do not sell maps for this type of collectible. Luckily, they are all fairly close together in Buckingham, Westminster. Use eagle vision when near their location and they will show up on the map. If you buy the skill upgrade that increases eagle vision range the hunt for collectibles will get easier. You can buy treasure maps for chests, beer brands, historical posters and pressed flowers from merchants (e.g. from the black market merchant in your train).

All Royal Letters are saved automatically when picking them up. On the map you can see how many you have found.

Look Out Below
Kill three enemies with a single stack of hanging barrels.
A perfect place for this trophy / achievement is at the start of Sequence 4 – Memory 2. There’s one enemy standing under hanging barrels and two others will come to talk to him. Shoot the barrels with your pistol when they are standing underneath. It will instantly kill them.
You can replay this mission any time! From the main menu go to “Progression Log” – “Progress Tracker” to replay it.

Queensbury Rules
Reach combo level 40.
This trophy / achievement is best done in fight clubs. The first one is unlocked in the borough “City of London”. Talk to Robert Topping, he is marked with a “T” symbol on the map. Progress to the last round and you should have more than enough enemies to get a x40 combo. Avoid being hit to keep your combo streak (counter when the bar above an enemy’s head is flashing yellow).
If you are already on a high character level you should visit one of the harder fight clubs, otherwise the enemies might die too quickly.

Opium Scourge
Affect at least four enemies simultaneously with the Hallucinogenic Dart.
You get the Hallucinogenic Darts in Sequence 4, Memory 4. This memory is also a perfect place for the trophy / achievement. The only way to affect four enemies simultaneously is to shoot the darts into a fire source. The darts will then disperse their effects over a greater area. Alert several enemies and lure them to a fire source. Counter their attacks until 4+ enemies are standing right next to the fire source. Now climb onto any structure and shoot the dart into the fire.
Please note that you cannot aim the darts while in ground combat (only quick fire works). That’s why you should climb onto a structure, it will let you aim the darts manually. If something goes wrong you can reload the last checkpoint.

Needle in a Haystack
Kill five enemies from within the same haystack.
Works great in Sequence 6 – Memory 2. At the very start of this mission you must investigate 3 weapon crates. Go to the middle one. You’ll find a haystack here, jump in from the building above. Two guards are standing by the haystack. Another will walk past it after half a minute. The last two enemies are patrolling the area, whistle to lure them to you (press D-Pad down). Make sure nobody sees how you assassinate someone from inside the haystack, it will blow your cover.
You are even allowed to leave the haystack and whistle at other enemies to lure them to you.

Artisan
Craft a Level 10 Item.
To craft a level 10 item you must first get the schematic and unique material. Schematics are rewards for game completion and can also be found in locked chests. Unique materials are obtained from locked chests (fixed locations) and by completing certain side quests.
A good and easy choice for the trophy / achievement is “Aegis Cloak”. You get the schematic for beating the final story mission (Sequence 9 – Memory 4). The unique material “Golden Spider Silk” can be found in the Strand borough from a locked chest.