In chapter 966 Shanks has his first encounter with Marshall D. Teach. According to Buggy, it is said that Teach has never slept during his life!
This seems connected to the fact that Teach has a strange and special body compared to ordinary people.
What could this possibly mean? Is it related to the ability of eating 2 devil fruits?
This information seems to confirm the theory according to which Blackbeard has multiple (3) personalities.
1- THE DREAM-FOLLOWER
2- THE EVIL PLANNER
3- THE COWARD
Him never sleeping suggests that one of his personalities is always awake and in control.
It will be interesting to learn more about Teach as the story moves forward. So far we know that Teach is an orphan and he joined the Whitebeard Pirates when he was 12. He sailed with them for decades, he had the potential to be one of the Whitebeard Commanders and at some point after Roger’s death he fought Shanks and gave him the scars on his eye.
Ever since then Shanks has been worried about Teach, because Shanks himself was probably quite strong already back then and he probably sensed something strange and dark in Teach.