Karl is one of the Old Ones, ancient demons from the past, he fought humanity in the First War centuries ago. He survived but was banished along with his fellow demons.
Throughout the years that followed, certain witches tried to free Karl and the other Old Ones. They succeeded in May twenty-fourth in 2006 when the Nazca gate was broken open by Diego Salamanda and Karl and the other Old Ones crawled through the dimensional portal onto Earth. Karl saw Matt and watched him fight Chaos; Karl felt Chaos' pain and howled in agony. But Chaos knocked Matt out, and Karl and the other demons turned into two suns and teleported to Antarctica.
In 2008, Scarlett Adams was called to Hong Kong. Her stepfather said he had some problems requiring her attention. In reality, her stepfather betrayed her by giving her Karl as her bodyguard, and Audrey Cheng, a fellow Old One, as her guide.
Karl was very silent and menacing, and when the official at passport control asked about whether Karl should look after Scarlett, Karl just walked up to him, put his hand on the man's shoulder, and brainwashed him into believing he was alright.
Karl was very feared by the locals; nobody gave him any parking tickets or accosted him.
When the Triads killed Audrey Cheng, Karl was out of Scarlett's sight for awhile, but when her stepfather finally revealed her to the enemy, Karl appeared out of nowhere, picked up Scarlett, and threw her to the ground, smashing her head, and indirectly being the cause of Hong Kong's destruction as her power, a typhoon, came at that moment.
In the war
Karl returned to Oblivion, the palace of the Old Ones in Antarctica, and he fought with the Old Ones, in his true form, (which was unseen) in the war. He was expelled into Hell and presumably annihilated with the nuclear rockets sent in.
Karl had many powers. He was a fairly low-ranking Old One, but he was still frightening. His main powers were
- Brute strength