Culen (a.k.a. Colin; Cuilén mac Illuilb; Cuilean; or Culen the Whelp) was King of Alba from 967 to 971. The wider picture in Scotland at the time is set out in our Historical Timeline.
Culen was King Indulf's son and had believed himself to be his father's rightful heir, even when the crown had gone instead under the law of tanistry (in effect a vote by the senior members of the extended family) to King Duff. Culen had fought Duff for the crown and lost, and many Scots at the time felt Culen to be implicated in Duff's murder in Forres in 967.
King Culen was not around for long enough to make any really lasting impression on his country. Much of his time was spent in trying to regain control over Strathclyde, whose sub-king Riderch was taking an increasingly independant stance. During his campaigning, Culen killed Riderich's brother and raped his daughter.