The Sleeper is a series of robots created for the Red Skull by Nazi scientist. The most powerful Sleeper was the Fourth Sleeper because it had the ability to control its density and had the ability to become a living volcano. It was controlled by a sonic crystal key and the Sleeper would respond to the brainwaves of the individual holding it. The Sleeper was activated when the Red Skull was given the crystal key by a Nazi named Von Krimm. Captain America was being held captive at the time and saw the awakening of the Fourth Sleeper first hand. The Red Skull had a difficult time controlling the Sleeper and was attacked by Nazi soldiers. During the chaos, Captain America escaped and managed to take the crystal key away from the Red Skull. The Sleeper erupted again causing the Red Skull's secret shelter to collapse and seawater began to flood the base. The Red Skull had disappeared and Captain America resurfaced with the crystal key.
The Sleeper was located by Shield technology and it was discovered underground causing massive eruptions threatening to destroy everything on the seacoast. Captain America and Sharon Carter also known as Agent 13 arrived near the location of the Sleeper. The Sleeper then changed his molecular composition so he could move effortlessly through the solid rock towards the sonic key. The Sleeper finally surfaced and was coming towards Captain America and Agent 13. Cap gave the sonic key to Sharon Carter to hold while he engaged the Sleeper in battle. During the battle, Sharon began to worry about the man she loved and it began to take its toll on the Sleeper. Her worry over Cap began to transmit the emotion of fear into the Sleeper. Suddenly the Sleeper grabbed Captain America and had a stone like grip on him. Sharon thought this would be the end of Captain America and she desperately called for him. She was holding the crystal key during her emotional torment and suddenly it began to vibrate. The Sleeper began to stagger and faded away. Sharon’s desperate fear of losing the man she loved triggered the Sleeper’s apparent demise and the crystal key shattered in her hands.
Years later the fourth Sleeper was spotted outside of Waltham, Massachusetts. Captain America discovered him in the exact same location where he faded away decades earlier. The Sleeper was inactive and transported to Hangar 3, a special containment unit on Avengers Island. The Sleeper was about to get transferred to a stasis field when it suddenly came to life and started attacking Captain America. The man robot known as Machinesmith had beamed his intelligence into the Sleeper and took control of him. However, Captain America was able to attach a stasis field generator onto the Sleeper’s body and it neutralized the Sleeper’s circuits. Machinesmith escaped before the Sleeper was neutralized.
Recently the fourth Sleeper reappeared as a member of the Skelton Crew. Machinesmith had recovered the damaged Sleeper and was able to repair him. He then beamed his intelligence into the Sleeper’s body and acted as the muscle for the Skeleton Crew.
Powers and Abilities:
The fourth Sleeper was more powerful than all previous Sleeper robots combined. The fourth Sleeper had the ability to alter its density allowing it to move through solid objects and become intangible. It also had superhuman strength and durability. It could withstand attacks from various firearms and blows from Captain America’s shield. It also had the ability to erupt like a volcano and destroy anything in its path.
However the fourth Sleeper lost the ability to alter its density and volcanic powers after Machinesmith beamed his intelligence into the Sleeper’s body.
