Cole Turner

Cole Turner was born to a Demon Mother and Mortal Father which resulted in a half mortal half Demon child. Cole's Demon half went by the name of Belthazor.     Belthazor was an upper level demon who worked for the Triad. His mission was to infiltrate the Halliwell's and to discover their weaknesses and how best to kill them, he did this using his human side Cole who was an Assistant District Attorney (ADA).    Cole managed to win over their trust but Prue always suspected him. Over time he found it harder and harder to kill them as his love for Phoebe grew stronger.    When the Charmed Ones discovered that Cole was the demon they had been searching for Phoebe told her sisters that she vanquished him when infact her love for him compelled her to let him go.    Cole's love for Phoebe didnt keep him away for long and he returned months later on the run from The Source and willing to give up his powers so that he could become fully mortal and be with Phoebe properly.  Cole gave up his powers and became fully mortal but when the Charmed Ones finally vanquished The Source his powers filled the void in Cole where his Demon half once was and so Cole became the next Source.    While The Source Cole managed to sway Phoebe to the dark side and so she became the Queen of the Underworld carrying the Sources Demonic Spawn.    It didnt take long for Phoebe's good side to surface when she realised she must help an innocent. This managed to lure her back to the good side, she lost the baby when the Seer decided to carry the child herself but could not handle its power.    Cole was eventually vanquished in 'Centennial Charmed' the 100th Episode. Cole became an avatar unknown to the Charmed Ones and altered reality in hopes of getting Phoebe back and to make it that the Charmed Ones were never reconstituted and never met their sister Paige. Cole was disappointed when Paige found a way around this and Phoebe managed to finally rid herself of Cole for good.