The Krulius wore coarse, dark robes and a hood. Its breathing sounded harsh and wet through the hood and it smelled bad. It never seemed to sleep or even get tired.
The Krulius collected aliens from specific locations across the Galaxy. Among his captured aliens were a Graske, an Uvodni, a Sontaran, a Bane and a Slitheen. The Krulius stored his captured aliens digitaly on his own data-pods. A Ven Kyuk Nar pilot worked for the Kruluis and flew with him through the asteroid belts between Mars and Jupiter. However, the ship crashed on Earth and the Krulius left the pilot to die.
The Krulius was using a digital bio-converter to convert himself and the aliens in his data pods into digital bio-data. Mr Smith was able to track down the aliens, but he couldn't send the Krulius back to his home planet Dothos. The Krulius appeared inside the attic of 13 Bannerman Road.
Meanwhile the pilot was saved by Sarah Jane and Luke Smith and brought to the attic. Because the pilot supported Sarah Jane and her friends, the Krulius attacked the pilot with his toxic breath and teleported the pilot and Sarah Jane to the Doloth Star Base. He wanted them to watch how he would destroy the Earth. However Sarah Jane Smith was using her Sonic lipstick to send a signal to Mr Smith, who sent the location of the Krulius to the Judoon. A short time later Captain Tybo and several other Judoon arrived. They caught the Kruluis and put him to their prison ship. (COMIC: Monster Hunt)
The Krulius managed to escape from the Judoon, by using a sergically implanted teleport matrix in his arm. He took clone cell samples of his former captured aliens with him, which allowed him to grew perfect copies of these aliens, that were all completely in his power. The Judoon did not realise this. The Krulius went to his secret starship which was hidden behind a force warp in orbit. A while later he teleported Rani Chandra onto the ship. There Rani saw serveral captured aliens: a Slitheen, a Judoon, a Sontaran, a Bane, a Judoon and a Veil, which Rani thought was Androvax. Several Urglanic Shapeshifters were working for the Krulius and were making Rani believe that they were Clyde Langer. However Rani soon realised that they weren't Clyde and managed to escape from the ship. (COMIC: Return of the Krulius)
The Krulius led an army of alien slaves who attacked Sarah Jane's house. When Clyde defeated several of the aliens, the Krulius ordered the army to retreat. In the army were two Slitheen, three members of the Assault Force Delta, two Bane, three Judoon, a Graske, an Uvodni, who was called General Kudlak. The Krulius and his army teleported away however the Krulius told Sarah Jane that he would return. (COMIC: Defending Bannerman Road)