Complex sentence: Kur is an ancient Sumerian cryptid said to be a source of unlimited power and immortality for whoever can find and capture it, the first season focusing on it due to its ability to control all other cryptids which makes it a devastating threat in the wrong hands.
Split into simpler sentences: Kur is an ancient Sumerian cryptid said to be a source of unlimited power and everlasting life for whoever can find and capture it. The first season focuses on the search for the creature, since its ability to control all other cryptids made it a devastating threat in the wrong hands.