There are several popular characters associated with the Thousand Sons in Warhammer 40,000 lore. Here are a few examples:
Ahriman - Ahriman is one of the most well-known characters in the Thousand Sons army. He is a powerful sorcerer who was responsible for the infamous "Rubric of Ahriman," which turned most of his legion into dust. Ahriman is known for his relentless pursuit of knowledge and his desire to unlock the secrets of the universe.
Magnus the Red - Magnus is the Primarch of the Thousand Sons, and he is one of the most powerful psykers in the Warhammer 40,000 universe. Magnus is known for his incredible psychic powers, his imposing physical presence, and his tumultuous relationship with the Emperor of Mankind.
Scarab Occult Terminators - The Scarab Occult are a group of elite Terminators within the Thousand Sons army. They are highly skilled and heavily armed, and they are known for their ability to teleport into battle using their Rubricae armor.
Exalted Sorcerers - Exalted Sorcerers are powerful psykers within the Thousand Sons army who have ascended to the rank of sorcerer through their mastery of psychic power. They are highly skilled and have access to a wide range of psychic powers, making them a formidable force on the battlefield.
Daemon Princes - Daemon Princes are powerful Chaos entities that have been transformed by the power of Chaos. Many of the Thousand Sons' most powerful sorcerers have ascended to become Daemon Princes, giving them immense power and durability on the battlefield.