Talent-Swallowing Magician

It is a magic and Magician manhwa, where Main character is sole heir of the prestigious magic family, which is also known as strongest Magicians family.
But in a war with Demon king and his Army; it lost almost every member, leaving only our MC and his older sister.
MC is talented, but due to a disease he can’t use magic.
To restore his family back to where it was he have to be Magician, but With the disease; he cant become a magician.
And that’s when the pandent left by his family ancestors, which can swallow demons magical talent swallowed a demon king.