Red Gems (アカダマ, Akadama) are special items featured in Shadows of the DAMNED. They are rare, blood-red jewels which can be used to purchase various upgrades for Garcia and Johnson. Red Gems are highly illegal performance-enhancers in the underworld and trafficking operations are routinely busted by the Gem Enforcement Agency.
There are a total of 80 Red Gems in the game; of these, 38 are hidden throughout the levels, while the remaining 42 must be bought from Christopher. Collecting all 80 Gems will reward the player with the 'High in Las Vegas' achievement/trophy.