To unlock IX Diego (Zombie Character) in Black Ops 4 Blackout, you need to play find the Mayan Crest, use a Bowie Knife to take out another player and complete the match in any place. If you fail to complete the character mission for any reason in one match, you need to find the IX Diego’s Mayan Crest in the next game again.
IX Diego’s mission item can be found in Equipment Stashes
HOW TO GET THE MAYAN CREST
The wind towers are a great place to look for equipment stashes. Grab a vehicle and farm them one by one to get the Mayan Crest.
BOWIE KNIFE LOCATIONS
Aside from the Equipment Stash, the Bowie Knife can be found in Zombie locations as Zombie drops and floor loot