The Hypnobrai Tomb is located in the Glacier Barrens, hidden from view by the raging blizzards and piles of snow. The entrance bears a carving resembling the face of a Hypnobrai General, and the tomb itself is mostly made of ice. There appear to be multiple layers to the tomb, accessible through large crevices in the ice.
After Lloyd's candy raid in Jamanakai Village was foiled by the Ninja, the would-be evil overlord was forced to flee into the Glacier Barrens after being assaulted by the angry villagers. While swearing revenge on the Ninja for his previous defeat, Lloyd spotted a strange marking under the snow, which turned out to be the entrance to the Hypnobrai Tomb.
After uncovering the door, Lloyd opened the tomb by pulling a lever shaped like a small snake, causing him to slide into an icy cavern. While investigating the tomb, he was confronted by Slithraa, General of the Hypnobrai. Slithraa attempted to hypnotize Lloyd, only for the boy to slip on the ice, causing Slithraa's hypnotic gaze to reflect back at its sender. With the Serpentine General dazed and susceptible to suggestion, Lloyd told Slithraa to obey him, indirectly gaining the allegiance of the entire Hypnobrai tribe.
The Hypnobrai subsequently left their tomb to return to Jamanakai Village, where they helped Lloyd resume his candy raid. When the Ninja interfered and stole Slithraa's Hypnobrai Staff, Lloyd called a retreat back to the Hypnobrai Tomb.
Shortly after the failed attack on Jamanakai Village, Lloyd had Slithraa send the Hypnobrai to Wildwood Forest, where they were put to work building a treehouse for the would-be evil overlord. When the Ninja attacked, Skales betrayed Lloyd and led the Hypnobrai to the Monastery of Spinjitzu, burning the place to the ground and retrieving the Hypnobrai Staff before retreating to the Hypnobrai Tomb.
Back in the tomb, Lloyd ordered Slithraa to reassert his authority and get the Hypnobrai to set Lloyd free. However, Skales refused, instead challenging Slithraa to a Slither Pit for leadership of the tribe. As the battle raged, Lloyd spotted a map in a nearby ice crevice, which he managed to steal in between cheering on Slithraa. Unfortunately, Slithraa was eventually defeated by Skales, who used his new authority to secure Slithraa's allegiance and banish Lloyd from the Hypnobrai Tomb.
LEGO Ninjago: Masters of Spinjitzu
Season 1: Rise of the Serpentine