They're called the Descendants. They were originally the Spaniards who went after El Dorado in Uncharted: Drake's Fortune (the big golden statue you see there), but were turned into those monsters for the treasure was cursed.
By the way, spoilers But really, if you haven't played the game by now that's your fault. It's years old now, your loss.
Come check out my Twitch TV channel, will be streaming various PS4 games from time to time http://www.twitch.tv/reddaxel