How do you unlock black costume in assassins creed 2?

Answer 1

There were two black robe sets in ACII - Ezio's standard robes could be dyed wetland ebony, and the Armour of Altair were black by default.

-You could dye Ezio's robes Wetland Ebony at one of the tailors in Forli

-Altair's robes could only be unlocked after all 6 assassin seals were acquired and placed in the crypt beneath the Villa Auditore

Answer 2

You can do this by unlocking a code in the extra content. You can get this code by buying the Assassin's Creed II mobile game, and they are also included in the Digital Deluxe Edition and the Game Of The Year edition