Krislok was a Graske who enountered Sarah Jane Smith and her friends.
History
Krislok was drving his space shuttle when it started to burn up he was aprouched by The Trickster who said if he joined him then he would end up getting saved from death. His first task was to remove Maria Jackson from time as she had figured out what had happened to Sarah Jane when the Trickster had removed her from time. He lost her from his grasp and failed. (SJA: Whatever Happened to Sarah Jane?)
Krislok's next task was to pose a an eleven year old boy from 1951 He then opened a gap in time and ran through it so that he could tempt Sarah Jane into coming back and meet her parents who died on 18th August 1951. He was sent back by her and her friends and he told Sarah Jane that it was July 1951 not Agust so that she could tempt him. Meanwhile in the 21st century Sarah Jane and Luke travelled to 1951 to meet her parents he asked the Trickster if he had done well and he did so. Rani and Clyde found the Puzzle Box in Sarah Jane's attack and go to the mall where the time portal opened. Krislok detected it and ran into the 21st Century to find them as time has changed as Sarah Jane dsiabledd her parents car. Everything started to turn into a wreck in the future the only people left where Clyde and Rani in the future.