Heimdall, the Watcher, is a character from Norse mythology who is in charge of protecting the Bifrost, the bridge between the worlds. He is considered one of the most powerful gods and is known for his ability to detect any threat to the security of the realm of Asgard. He possesses keen senses and perfect eyesight that allows him to see everything that happens in the Nine Realms. In addition, Heimdall also possesses a magical horn called the Gjallarhorn with which he can warn all the gods in case of danger.
It is considered as the guardian of the Bifrost and is meant to protect it against any external or internal threat. He is responsible for maintaining the security of the kingdom and also has the ability to open the gates between the worlds if he so desires. It is said that Heimdall is as powerful as Thor and Odin combined, which shows his importance within the Norse pantheon.