Semek is a magical stone just like Depore. It has great power, and once a pact is formed with it's controller, the controller gains unbelievable power.
Semek is a stone that reacts only to demon power. Semek takes on a human-like form in the shape of a man in his early twenties when emerging from the stone. He wears loose clothing and has markings on his skin. His complexion is tan with blond hair. Whoever is in possession usually loses self-control and goes on a rampage. Semek is bloodthirsty, but shows concern for whoever is his master. It is rather unsettling how dissonant Semek's attitude is when it comes to the battlefield. Whereas his wielder will fall into a crazed frenzy to battle Semek is the polar opposite and seems amused with the carnage happening around him. While the battlefield is erupted in chaos and warriors are falling one by one Semek just smugly observes his wielder's abilities.
When in demon form he takes on the form of a rod connected by two huge swords. In Immortal Regis and Cavalier of the Abyss, Serin is shown possessed by Semek and goes on a rampage. Out the six great devil stones, Semek is the most powerful magic stone as Caladbolg was unable to take control of it and therefore is the only stone that was capable of killing Caladbolg.
It's current location
When Serin escaped from the castle, she took Semek with her. She then visited the Baanan Clan Village and left Semek along with baby Xix with the village Chief. When Xix made a contract with the demon Skull, he left Semek in the possesion of Osky. Now Osky currently holds possesion of Semek.
Semek is only shown for a brief appearance in Cavalier of the Abyss where he watches Serin confront her enemy with amusement. His personality was established in Immortal Regis so information listed is from the original series. Semek found teenage Serin's stubbornness amusing and claims she is an interesting person when she challenges him for possessing her during a battle. Semek shows no qualm with possessing Serin whenever he feels his wielder needs help or he's bored. Initially, Semek was going to allow Serin to die- during her battle with a stronger opponent - until he sees through Serin's memories her resolve for finding reasons to live. He seems intrigued by Serin's sudden interest in living after she saved a dying Jae-Hyuk (now Regis Nex) after the young man fought to survive after being hit with a fatal blow. Hearing Serin proclaim she wished to live finalized Semek's decision to save her. While he shows concern for Serin he is not above acting haughty towards her and humbling Serin by reminding her that while she is powerful she is not an ancient being with his level of power and knowledge. Semek is teasing in nature and seems more composed in comparison to hot-blooded, childish Depore and formerly unstable, malicious Caladborg.