Sleeper is a plot-device character in Tomb Raider: The Angel of Darkness.
Sleeper is one of few remaining Nephilim. The Cabal had retrieved the last Nephilim specimen from subterranean city of central Cappadocia in Turkey: a Nephilim body which had been nicknamed the Sleeper. The Cabal is trying to use the Sleeper as a means to revive the Nephilim race. One of the earliest tries of the project was the failed Proto-Nephilim.