To get this achievement you need to find special items located in random areas on the map.
When you have these items you can look at them in your inventory to see what challenges you must complete during that match to unlock the character. You need all 4 for the achievement.Note:
Placements may vary depending on if you're playing Solo, Duo, Quads so make sure you check what exact placement you have.
And of course challenges must all be done in the same game that you find the item.Woods:
Find "Bandanna" from BO1 Campaign Helicopter Spawn location North of Firing Range on Top of the Brown Box
-Ride in a Helicopter for at least 30 Seconds to a minute
-Win the match with "Bandanna" in inventory
(You must be ALIVE. Your teammates can get the final kill but you need to be alive for it to count as the challenge states “You Can’t Kill Me!”)
Note: with the new limited time game-mode “Ground War” being a 50 vs 50 mode it makes it much easier to be able to win. So keep an eye out for when this mode is running if you’re struggling. Menendez:
Find a "Locket" item from a Supply Drop
-Kill 2 enememies with a Shotgun
-Finish the match with Locket item in your inventory
A Shotgun kill on a downed enemy DOES count.Reznov:
Find "Ushanka Hat" in Estates around the Fountain Statue, around the Red Art Statue, or at Asylum in the empty corner fountain.
-Kill an enemy at “Long Range” (200meters or more)
-Place Top 2 in Quads, Top 3 in Duos, Top 5 in Solo
-Finish the match with "Ushanka Hat" in your inventory
(A Mesh Mine kill from a long distance won’t count and it seems that a Rocket Launcher kill on a vehicle from 200+ meters also won’t count anymore)Mason:
Find "Stained White T-Shirt" from a Supply Stash
-Wake the Sleeper Agent (Start the Emergency Alert at Array by pressing the lit up machine in the main building)
-Place Top 4 in Quads, Top 8 in Duos, Top 15 in Solo
-Finish the match with T-Shirt in your inventory
This fortunately can be activated again for this challenge even if someone already did it.
Video of the how to activate the Emergency Alert credit to randomChievos
Thanks for help from Was I That Bad, Ex GHOSTface, DANIELJJ14, WizZy PL, Luuc, SSSteinMan and Itzz Sh0wt1m3